Partially covered door will be shown atop covering pieces when animated

Steps to reproduce:
1. Put some tiles to cover doors.
2. Make them open via trigger, or put them on the start screen.
3. The animated parts will be shown.

Illustration video: http://oscomp.hu/depot/sdlpop_covered_exit_glitch.mkv

Note: The same happens in the original game, but i still think, this should be fixed.