Bug 156865 Undo / Redo marker actions not updated
I20060906-1200 If a file gets delete after adding/changing/removing a marker then the Undo and Redo actions are not updated and still show, e.g. Undo Add Task Redo Add Task Executing the undo or redo does nothing (no feedback, no .log entry) and the undo and redo menu text remains the same and enabled.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/undo/AbstractMarkersOperation.java
* 
	 * This is an optimization that allows us to add specific undo contexts for
	 * tasks and bookmarks, without also adding the workspace undo context. Note
	 * that clients with different marker types may still assign their own
	 * specific undo context using AbstractOperation.addContext(IUndoContext) in
	 * addition to the workspace context assigned by this method.
	 */
	private void addUndoContexts() {
		String[] types = null;
		if (markers == null) {
			if (markerDescriptions != null) {
				types = new String[markerDescriptions.length];
				for (int i = 0; i < markerDescriptions.length; i++) {
					types[i] = markerDescriptions[i].type;
				}
			}
		} else {
			types = new String[markers.length];
			for (int i = 0; i < markers.length; i++) {
				try {
					types[i] = markers[i].getType();
				} catch (CoreException e) {
				}
			}
		}
		if (types != null) {
			for (int i = 0; i < types.length; i++) {
				if (types[i].equals(IMarker.BOOKMARK)) {
					addContext(WorkspaceUndoSupport.getBookmarksUndoContext());
				} else if (types[i].equals(IMarker.TASK)) {