Fix custom compat emulator

[Lucki]

Some fixes when using a custom emulator with a compat tool (Proton):

• When an emulator is started without a game e.g. from the settings dialog then the silently called compat run dialog is missing some null checks for the emulated_game.
• After initialization the work_dir for an emulator is never refreshed resulting in being an unexpected null further down the line for emu.work_dir at https://github.com/tkashkin/GameHub/blob/ebb46ff0b394fbb004e8a3d2bfc4f47410dec18f/src/data/compat/Wine.vala#L159 The refresh logic is a (almost) direct copy from Game.vala.