Get rid of Command Undo Not Valid

A continual irritant is to make a mistake while entering text, hit CNT-Z, and get the little three-blip "think twice fella" chime and the message Command Undo Not Valid in Current State. Maybe it has to work this way for some reason in MuseScore, but in the user interface "vernacular" there's a strong intuitive assumption that if you are in text editing mode, make a mistake, and don't get out of text editing mode, CNT-Z will undo the last text entered instead of giving you an error message. It would be a better user experience if CNT-Z while in text entering mode worked in MuseScore the way it works almost everywhere else.