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
*         if it is not.
	 */
	boolean hasContext(IUndoContext context);
	/**
	 * Redo the operation. This method should only be called after an operation
	 * has been undone.
	 * 
	 * @param monitor
	 *            the progress monitor (or <code>null</code>) to use for
	 *            reporting progress to the user.
	 * @param info
	 *            the IAdaptable (or <code>null</code>) provided by the
	 *            caller in order to supply UI information for prompting the
	 *            user if necessary. When this parameter is not
	 *            <code>null</code>, it should minimally contain an adapter
	 *            for the org.eclipse.swt.widgets.Shell.class.
	 * @return the IStatus of the redo. The status severity should be set to
	 *         <code>OK</code> if the redo was successful, and
	 *         <code>ERROR</code> if it was not. Any other status is assumed
	 *         to represent an incompletion of the redo.
	 * @throws ExecutionException
	 *             if an exception occurred during redo.
	 */
	IStatus redo(IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException;
	/**
	 * Remove the specified context from the operation. This method has no
	 * effect if the context is not equal to another context in the context
	 * list. Note that determining whether a context is present when removing it
	 * is based on equality, not whether the context matches ({@link