Bug 208791 [Markers] NPE in ExtendedMarkersView
org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.NullPointerException) at org.eclipse.swt.SWT.error(SWT.java:3706) at org.eclipse.swt.SWT.error(SWT.java:3624) [... snip ...] Caused by: java.lang.NullPointerException at org.eclipse.ui.internal.provisional.views.markers.ExtendedMarkersView$10.runInUIThread(ExtendedMarkersView.java:896) at org.eclipse.ui.progress.UIJob$1.run(UIJob.java:94) at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35) at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:130) ... 52 more This brought down testResourceMappings(), but you just need to check getCategories() can return null. PW
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/provisional/views/markers/ExtendedMarkersView.java
* 
	 * @return Clipboard
	 */
	Clipboard getClipboard() {
		if (clipboard == null)
			clipboard = new Clipboard(viewer.getControl().getDisplay());
		return clipboard;
	}
	/**
	 * Return the content provider for the receiver.
	 * 
	 * @return ITreeContentProvider
	 * 
	 */
	private ITreeContentProvider getContentProvider() {
		return new ITreeContentProvider() {
			/*
			 * (non-Javadoc)
			 * 
			 * @see org.eclipse.jface.viewers.IContentProvider#dispose()
			 */
			public void dispose() {
			}
			/*
			 * (non-Javadoc)
			 * 
			 * @see org.eclipse.jface.viewers.ILazyTreeContentProvider#getParent(java.lang.Object)
			 */
			public Object getParent(Object element) {
				Object parent = ((MarkerItem) element).getParent();