Weird Eclipse E4 RCP NullPointerException

Today i have tried to create a little eclipse e4 demo application to debug some issues with theme switching, but every time i switch the theme i got a strange NPE that the workbench instance is null. After some struggling with this problem i have found out that the root cause is, that i had still some eclipse RCP 3.x (org.eclipse.ui.workbench...) plugins in my launch configuration. So if you get such an error be sure to remove all RCP 3.x plugins from your launch configuration.

java.lang.NullPointerException
 at org.eclipse.ui.internal.themes.ColorAndFontProviderImpl.getCurrentTheme(ColorAndFontProviderImpl.java:51)
 at org.eclipse.ui.internal.themes.ColorAndFontProviderImpl.getColor(ColorAndFontProviderImpl.java:47)
 at org.eclipse.e4.ui.css.swt.helpers.CSSSWTColorHelper.findColorByDefinition(CSSSWTColorHelper.java:319)
 at org.eclipse.e4.ui.css.swt.helpers.CSSSWTColorHelper.getRGB(CSSSWTColorHelper.java:70)
 at org.eclipse.e4.ui.css.swt.helpers.CSSSWTColorHelper.getSWTColor(CSSSWTColorHelper.java:58)
 at org.eclipse.e4.ui.css.swt.properties.converters.CSSValueSWTColorConverterImpl.convert(CSSValueSWTColorConverterImpl.java:46)
 at org.eclipse.e4.ui.css.swt.properties.converters.CSSValueSWTColorConverterImpl.convert(CSSValueSWTColorConverterImpl.java:1)
 at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.convert(AbstractCSSEngine.java:1077)
 at org.eclipse.e4.ui.css.swt.properties.custom.CSSPropertye4TabOutline.applyCSSProperty(CSSPropertye4TabOutline.java:31)
 at org.eclipse.e4.ui.css.swt.properties.AbstractCSSPropertySWTHandler.applyCSSProperty(AbstractCSSPropertySWTHandler.java:40)
 at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyCSSProperty(AbstractCSSEngine.java:722)
 at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyleDeclaration(AbstractCSSEngine.java:520)
 at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyles(AbstractCSSEngine.java:413)
 at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyles(AbstractCSSEngine.java:354)
 at org.eclipse.e4.ui.css.swt.internal.theme.ThemeEngine.applyStyles(ThemeEngine.java:512)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$11.setClassnameAndId(PartRenderingEngine.java:1321)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.setCSSInfo(SWTPartRenderer.java:111)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.bindWidget(SWTPartRenderer.java:128)
 at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.createWidget(StackRenderer.java:620)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:983)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:662)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.SashRenderer.processContents(SashRenderer.java:185)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.SashRenderer.processContents(SashRenderer.java:185)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.SashRenderer.processContents(SashRenderer.java:185)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.SashRenderer.processContents(SashRenderer.java:185)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveRenderer.processContents(PerspectiveRenderer.java:49)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.showTab(PerspectiveStackRenderer.java:103)
 at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer$1.handleEvent(LazyStackRenderer.java:69)
 at org.eclipse.e4.ui.services.internal.events.UIEventHandler$1.run(UIEventHandler.java:40)
 at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:187)
 at org.eclipse.swt.widgets.Display.syncExec(Display.java:4590)
 at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:218)
 at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:36)
 at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197)
 at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197)
 at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
 at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
 at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
 at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135)
 at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78)
 at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39)
 at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:81)
 at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:59)
 at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:374)
 at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:135)
 at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:1)
 at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:108)
 at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.postProcess(PerspectiveStackRenderer.java:77)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:678)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:69)
 at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.processContents(WBWRenderer.java:663)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
 at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1074)
 at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:331)
 at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032)
 at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148)
 at org.eclipse.e4.ui.internal.workbench.swt.E4Application.start(E4Application.java:164)
 at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
 at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:380)
 at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:483)
 at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648)
 at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603)
 at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
 at org.eclipse.equinox.launcher.Main.main(Main.java:1438)