Fix toggling MMMMMM always playing Presenting VVVVVV

This would be fine, under the assumption that you could never reach the
menu from outside the menu. Well, now you can, so now this has to play
the correct song instead of track 6.

desktop_version/src/Input.cpp

@@ -597,7 +597,7 @@ void menuactionpress()
             }
             music.usingmmmmmm = !music.usingmmmmmm;
             music.playef(11);
-            music.play(6);
+            music.play(music.currentsong);
             game.savestats();
         }
         else if (game.currentmenuoption == OFFSET+5+mmmmmm_offset)