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
* </p>
	 * 
	 * @return the array of contexts
	 */
	IUndoContext[] getContexts();
	/**
	 * Return the label that should be used to show the name of the operation to
	 * the user. This label is typically combined with the command strings shown
	 * to the user in "Undo" and "Redo" user interfaces.
	 * 
	 * @return the label
	 */
	String getLabel();
	/**
	 * <p>
	 * Returns whether the operation has a matching context for the specified
	 * context.
	 * </p>
	 * <p>
	 * This method may be called by the operation history from inside a
	 * synchronized block. To avoid deadlock conditions, implementers of this
	 * method must avoid dispatching and waiting on threads that modify the
	 * operation history during this method.
	 * </p>
	 * 
	 * @see IUndoContext#matches(IUndoContext)
	 * 
	 * @param context
	 *            the context in question
	 * @return <code>true</code> if the context is present, <code>false</code>