Add protected pop() method to QUndoStack

Every time I need to add some extended functionality like committing command stack from local PC to global server I have to include private headers and implement this very simple pop() (delete command(0) to the QUndoStack.

Why? Because when things go wrong and some commands leaves undone all I can do is to clear the stack and show message box with error icon.
canUndo method is not marked as virtual, so I can't just mark some commands can not be undone. Also I can't setIndex() without calling redo() so I have to mark all messages from server by some ID to prevent executing same redo() operation twice. This is ridiculous!