cataclysmDDA: filter out things that do not have for{Tiles,Curses} attrs

pkgs/games/cataclysm-dda/pkgs/default.nix

···
   if isNull build then
     true
   else if build.isTiles then
-    mod.forTiles
+    mod.forTiles or false
+  else if build.isCurses then
+    mod.forCurses or false
   else
-    mod.forCurses;
+    false;
 in
 
 lib.makeExtensible (_: pkgs')