Skip rendering of OBJ_NONE objects to avoid a failed Assert (can happen when playing a demo then going to the editor)

CHANGELOG.txt

@@ -4,6 +4,7 @@ D1X-Rebirth Changelog
 --------
 main/gameseq.c: Allow level progressing if playing the builtin mission with EDITOR compiled - only exit if Current_level_num is 0
 editor/med.c: Reset the player object for the editor, since demo playback mucks it up
+main/render.c: Skip rendering of OBJ_NONE objects to avoid a failed Assert (can happen when playing a demo then going to the editor)
 
 20120416
 --------

main/render.c

@@ -1243,6 +1243,9 @@ void build_object_lists(int n_segs)
 				int new_segnum,did_migrate,list_pos;
 
 				obj = &Objects[objnum];
+				
+				if (obj->type == OBJ_NONE)
+					continue;
 
 				Assert( obj->segnum == segnum );