#239 Pressing Ctlr-Z to Undo while clicking and dragging has undefined behavior

[William Kendrick]

Example: Click and drag with Emboss, then, without releasing the mouse button, press Ctrl-Z on the keyboard to undo.

[Pere Pujal i Carabantes]

Avoiding CTRL-Z action in certain situations should get ride of this

[William Kendrick]

A good way to reproduce the issue is to use paint brush. Click, drag, and (without releasing the mouse button) hit Ctrl-Z. The lines you draw disappear. Continue moving the mouse, and more lines will appear. You cannot Ctrl-Z, nor can you Undo at this point.

Your patch overcomes this. Thanks! :)