sol.menu.start() should make an error if the menu is already started
Created by: christopho
For now it silently starts the menu a second time, creating nasty bugs like https://github.com/solarus-games/zelda-xd2-mercuris-chess/issues/2
Created by: christopho
For now it silently starts the menu a second time, creating nasty bugs like https://github.com/solarus-games/zelda-xd2-mercuris-chess/issues/2