Add a proper error screen, like neoSphere

[fatcerberus]

1e8f5d8 adds handling for errors thrown out of Dispatch jobs; in case of an uncaught exception, all Dispatch jobs are canceled and the error is displayed in a box underneath the game screen. This helps to ensure the game doesn't end up in a zombie state after an error, but isn't particularly user-friendly.

Ideally, the game would switch to an error screen, as happens in neoSphere after an uncaught exception. This makes it clear to the player that the game crashed; the current behavior can make it seem like the bug is in the engine itself rather than the game being played.