Some modal dialogs are not centered on the screen when the window resizes
Certain modal dialogs, such as the confirmation dialog that appears when selecting "Exit", are no longer centered on the screen after resizing the window. This may cause them to go off-screen entirely.
Steps to reproduce: Load a game and select "Exit" Resize the window via the window manager's frame
(RM-2289 from redmine: created on 2015-01-21 by scrawl ., , closed on 2017-02-14 by scrawl .)