Assert.isTrue(comment == null || !"".equals(comment));
	public void setRefactoringComment(final RefactoringDescriptorProxy proxy, final String comment, IProgressMonitor monitor) throws CoreException {		Assert.isNotNull(proxy);		Assert.isTrue(comment == null || !"".equals(comment)); //$NON-NLS-1$		if (monitor == null)			monitor= new NullProgressMonitor();		fUndoStack.setComment(proxy, comment, monitor);	}