(svn r10548) -Fix [FS#1020]: don't segfault when you quit in the end-of-the-game screen

src/main_gui.cpp

@@ -1700,7 +1700,7 @@ static void MainToolbarWndProc(Window *w, WindowEvent *e)
 	}
 
 		case WE_MESSAGE:
-			HandleZoomMessage(w, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, 17, 18);
+			if (FindWindowById(WC_MAIN_WINDOW, 0) != NULL) HandleZoomMessage(w, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, 17, 18);
 			break;
 	}
 }