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
for (int i = 0; i < markers.length; i++) {
			if (!markers[i].exists()) {
				return false;
			}
		}
		return true;
	}
	/*
	 * Return whether there is enough information specified in this operation to
	 * delete markers.
	 */
	protected boolean canDeleteMarkers() {
		return markersExist();
	}
	/*
	 * Return whether there is enough information specified in this operation to
	 * create markers.
	 */
	protected boolean canCreateMarkers() {
		return markerDescriptions != null && resourcesExist();
	}
	/*
	 * Return whether there is enough information specified in this operation to
	 * update markers.
	 */
	protected boolean canUpdateMarkers() {
		return attributes != null && markersExist();
	}
}