Fix lightning

Fixes #632
Error caused by buffer overflow in scenery load. I've added in some extra resets of lightning to prevent any small issues.

Note #635 is not related to this and it requires its own fix.
Its a flag so i've changed it from 1 to (1<<SCREEN_FLAGS_PLAYING). SCREEN_FLAGS_PLAYING is 0 so it becomes 1<<0 = 1.