Fix crashes when dragging and dropping files outside of the gamelist

Prior to this PR dragging and dropping games into a docked window other than the game list would cause the emulator to initialize incorrectly and crash due to an access violation from dereferencing a null pointer (thanks to JMC for pointing this out). Since the idea here is to initialize the game/compatible file regardless of its dropped location within the main frame, it makes sense to actually have this handling code within the Frame code.