Bug 218467 [Undo] Tighten up IUndoableOperation spec and AbstractOperation to discourage/prevent null labels
GMF creates CompositeCommands with null labels. These NPE when shortenText(getOperation().getLabel()) is invoked from update.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IUndoableOperation.java
* Returns whether the operation can be executed in its current state.
	 * </p>
	 * 
	 * <p>
	 * Note: The computation for this method must be fast, as it is called
	 * frequently. If necessary, this method can be optimistic in its
	 * computation (returning true) and later perform more time-consuming
	 * computations during the actual execution of the operation, returning the
	 * appropriate status if the operation cannot actually execute at that time.
	 * </p>
	 * 
	 * @return <code>true</code> if the operation can be executed;
	 *         <code>false</code> otherwise.
	 */
	boolean canExecute();
	/**
	 * <p>
	 * Returns whether the operation can be redone in its current state.
	 * </p>
	 * 
	 * <p>
	 * Note: The computation for this method must be fast, as it is called
	 * frequently. If necessary, this method can be optimistic in its
	 * computation (returning true) and later perform more time-consuming
	 * computations during the actual redo of the operation, returning the
	 * appropriate status if the operation cannot actually be redone at that
	 * time.
	 * </p>
	 * 
	 * @return <code>true</code> if the operation can be redone;