Unexpected Null pointer causing rcp theme lookweird - swt

Question

Suddenly the theme is getting a null pointer exception here is the stack trace has anyone seen such issue and resolved it. I am assuming some kind of race condition is occuring but I have not been able to pinpoint the cause.
java.lang.NullPointerException
at org.eclipse.ui.internal.themes.ColorAndFontProviderImpl.getCurrentTheme(ColorAndFontProviderImpl.java:51)
at org.eclipse.ui.internal.themes.ColorAndFontProviderImpl.getFont(ColorAndFontProviderImpl.java:35)
at org.eclipse.e4.ui.css.swt.helpers.CSSSWTFontHelper.findFontDataByDefinition(CSSSWTFontHelper.java:218)
at org.eclipse.e4.ui.css.swt.helpers.CSSSWTFontHelper.getFontData(CSSSWTFontHelper.java:163)
at org.eclipse.e4.ui.css.swt.properties.converters.CSSValueSWTFontDataConverterImpl.convert(CSSValueSWTFontDataConverterImpl.java:73)
at org.eclipse.e4.ui.css.swt.properties.converters.CSSValueSWTFontConverterImpl.convert(CSSValueSWTFontConverterImpl.java:34)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.convert(AbstractCSSEngine.java:1077)
at org.eclipse.e4.ui.css.swt.properties.css2.CSSPropertyFontSWTHandler.onAllCSSPropertiesApplyed(CSSPropertyFontSWTHandler.java:251)
at org.eclipse.e4.ui.css.core.impl.engine.AbstractCSSEngine.applyStyleDeclaration(AbstractCSSEngine.java:549)
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:514)
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:110)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.styleElement(SWTPartRenderer.java:80)
at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer$5.handleEvent(StackRenderer.java:524)
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:4734)
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.workbench.UIEvents.publishEvent(UIEvents.java:372)
at org.eclipse.e4.ui.workbench.UIEvents.publishEvent(UIEvents.java:341)
at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.activate(PartServiceImpl.java:652)
at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.activate(PartServiceImpl.java:615)
at org.eclipse.e4.ui.internal.workbench.swt.AbstractPartRenderer.activate(AbstractPartRenderer.java:106)
at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer$1.handleEvent(ContributedPartRenderer.java:61)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4353)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1061)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1085)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1070)
at org.eclipse.swt.widgets.Shell.setActiveControl(Shell.java:1453)
at org.eclipse.swt.widgets.Shell.setActiveControl(Shell.java:1416)
at org.eclipse.swt.widgets.Control.sendFocusEvent(Control.java:2855)
at org.eclipse.swt.widgets.Widget.wmSetFocus(Widget.java:2425)
at org.eclipse.swt.widgets.Control.WM_SETFOCUS(Control.java:5236)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4680)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:5023)
at org.eclipse.swt.internal.win32.OS.SetFocus(Native Method)
at org.eclipse.swt.widgets.Control.forceFocus(Control.java:1097)
at org.eclipse.swt.widgets.Control.setSavedFocus(Control.java:3619)
at org.eclipse.swt.widgets.Decorations.restoreFocus(Decorations.java:837)
at org.eclipse.swt.widgets.Shell.open(Shell.java:1248)
at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.postProcess(WBWRenderer.java:745)
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.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1074)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
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(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
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)

Answer 1

adding -clean flag to run-time configuration solves the issue but still no idea what is causing it. so I will appreciate a solution that a temporary fix

Answer 2

Add it to Run/ Run-Configuration/Arguments
-os ${target.os} -ws ${target.ws} -arch ${target.arch} -nl ${target.nl} -consoleLog -clean

Answer 3

First and foremost, It's a known Bug in Eclipse Bug 440763. It has something to do with the Eclipse version, since in 4.3 I wasn't facing the exception. It looks like a regression problem of the CSS-engine in Eclipse 4.4.
I don't know exactly what's the problem in there, but here is how I got rid of it.
Removing this plugin org.eclipse.ui.themes from dependencies (and from the target platform) solved the problem.
Go to Run Configurations -> Arguments -> Program arguments
Add -clearPersistedState
I guess, this wouldn't qualify as a response since I don't give any explanations, but it sure helps.

Answer 4

Go to C:\Users\USER\eclipse\ECLIPSE_VERSION\eclipse\configuration\config.ini
Open file config.ini
Add this line: osgi.clean=true
Start eclipse.
If it is working then delete this line afterwards.
This is same as -clean argument.
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