Map Editor: If you change map type from deathmatch to my pet dungeon, it doesn't allow mightyscript

Edit: It appears the problem is not deathmatch, but when you load a mpd map that has a mightyscript script in it, then when you try to run it, it says something like "this mode can't have a script".  However the mpd game type says mightyscript is allowed.

Original: If you create a new map and set it to deathmatch (default setting), then later, via the mightyscript icon, change it to my pet dungeon, then it appears that the game gets confused and it won't allow you to use mightyscript (off for deathmatch, on for mpd).