Fix partial UI soft-lock with certain in-game menus

[past-due]

Probably reproducible in several ways, but here's one:

1. Start a multiplayer game
2. Enable debug mode
3. Open the Script Debugger (but collapse / minimize it for now)
4. Press "ESC" to open the in-game menus
5. Open either the Keymap Viewer or the Music Manager
6. Restore the Script Debugger and click the "Add Structures" button
7. See the UI lockup

This whole section of the UI could use a rewrite / modern use of "overlay screens" and such. But a quick fix is to actually clean up those special in-game menus in intCloseInGameOptionsNoAnim()