Description Dominik G. 2020-01-14 07:38:35 EST

What steps will reproduce the problem?
1. Open a plugin.xml file in the Plugin Manifest Editor and select the Overview tab (or another view/editor with an ExpandableComposite)
2. Switch from the classic theme to the dark theme
3. Switch from the dark theme back to the classic theme
4. Change the size of the plugin.xml Editor
5. Every repaint of an ExpandableComposite causes the following error because the internally used colors were already disposed.

Exception Stack Trace:
java.lang.IllegalArgumentException: Argument not valid
	at org.eclipse.swt.SWT.error(SWT.java:4701)
	at org.eclipse.swt.SWT.error(SWT.java:4635)
	at org.eclipse.swt.SWT.error(SWT.java:4606)
	at org.eclipse.swt.graphics.GC.setForeground(GC.java:4344)
	at org.eclipse.ui.forms.widgets.Section.onPaint(Section.java:398)
	at org.eclipse.ui.forms.widgets.ExpandableComposite.lambda$0(ExpandableComposite.java:574)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:234)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4175)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1081)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1066)
	at org.eclipse.swt.widgets.Composite.WM_PAINT(Composite.java:1654)
	at org.eclipse.swt.widgets.Control.windowProc(Control.java:4816)
	at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:348)
	at org.eclipse.swt.widgets.Display.windowProc(Display.java:4827)
	at org.eclipse.swt.internal.win32.OS.RedrawWindow(Native Method)
	at org.eclipse.swt.widgets.Control.update(Control.java:4595)
	at org.eclipse.swt.widgets.Control.update(Control.java:4588)
	at org.eclipse.e4.ui.workbench.renderers.swt.SashLayout.lambda$1(SashLayout.java:100)
	at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:216)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4175)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3988)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3587)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1160)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1049)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
	at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:660)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:559)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:154)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:150)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
	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:657)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1465)