Set map.scrolldir when going to options in-game

This ensures that the background doesn't start scrolling the wrong way
in the menu.

desktop_version/src/Input.cpp

@@ -2120,6 +2120,7 @@ void mapmenuactionpress()
             game.createmenu(Menu::options);
         }
         map.nexttowercolour();
+        map.scrolldir = 0;
 
         // Fix delta rendering glitch
         graphics.updatetowerbackground();