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
addContext(WorkspaceUndoSupport.getTasksUndoContext());
				} else if (types[i] != null) {
					
					addContext(WorkspaceUndoSupport.getWorkspaceUndoContext());
				}
			}
		}
	}
	/**
	 * Return the array of markers that has been updated or created.
	 * 
	 * @return the array of markers that have been updated or created, or
	 *         <code>null</code> if no markers have been created or updated.
	 * 
	 * @since 3.3
	 */
	public IMarker[] getMarkers() {
		return markers;
	}
	/**
	 * Return whether the markers known by this operation currently exist.
	 * 
	 * @return <code>true</code> if there are existing markers and
	 *         <code>false</code> if there are no known markers or any one of
	 *         them does not exist
	 */
	protected boolean markersExist() {
		if (markers == null || markers.length == 0) {
			return false;
		}