[Dialog,Gtk] Alert intermittently reopens when closed with 'X' on Linux

To reproduce:

1) Run hello.HelloAlert
2) Click the "Toggle Color" button
3) Close the dialog with the red "X" button

Sometimes (maybe 1 out of 5 times on my system) the dialog will reopen during the process of closing it. If you press the cancel button, this does not happen. I've only ever seen this on Linux.