Fix: When trying to open fullscreen dialogs via the menu while paused, buttons in the bottom panel could get toggled erroneously.
Fix: Some issues remained after r1870 wrt. opening dialogs while building a room. Now, the window is only created if and when you click ok in the confirmation dialog.

git-svn-id: http://corsix-th.googlecode.com/svn/trunk@1878 c39591fa-788f-11de-a72b-d90af8dea425