The question has been closed Mar 12 '15 at 09:11 PM by Azarus for the following reason:
A button can only have a single child. Copy and pasting a button onto a button (by ctrl+c and ctrl+v while keeping the button selected) is infact an invalid action. Although the crash itself might just be a unescaped error.
Edit: You can actually nest buttons (just buttons) but once you add a text element you are filling the buttons max children restriction and locking it from recieving any more children (another button).
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