[Level Refactor bcc1aa95b] Titlemap breakage

[phantombeta]

Titlemaps appear to be having issues with event handlers, and possibly other map-specific things. Quite simply, it'll carry the event handlers over from the titlemap to the first level started. Starting the map again seems to fix the issue.
Loading save files also does not seem to exhibit the same problem, though I can't confirm it.

Attached is a simple titlemap with an event handler.
Steps to reproduce:

• Start GZDoom with the titlemap loaded.
• Start a new game. The titlemap's event handler and animation will persist onto the new game.

[Graf Zahl]

Fixed. The event manager wasn't fully cleared, leaving a reference to the already destroyed handler behind.