A_SetObjectFlags tweak

Only reset the sector/blockmap links on an object calling A_SetObjectFlags if the MF_NOSECTOR|MF_NOBLOCKMAP flags change. Fixes a freeze related to LD442 demonstrated in MascaraSnake's example WAD at https://dl.dropboxusercontent.com/u/27962790/statetest.wad .

src/p_enemy.c

@@ -7650,26 +7650,33 @@ void A_SetObjectFlags(mobj_t *actor)
{
INT32 locvar1 = var1;
INT32 locvar2 = var2;
+	boolean unlinkthings = false;
#ifdef HAVE_BLUA
if (LUA_CallAction("A_SetObjectFlags", actor))
return;
#endif
-	P_UnsetThingPosition(actor);
-	if (sector_list)
-	{
-		P_DelSeclist(sector_list);
-		sector_list = NULL;
-	}
-
if (locvar2 == 2)
-		actor->flags |= locvar1;
+		locvar1 = actor->flags | locvar1;
else if (locvar2 == 1)
-		actor->flags &= ~locvar1;
-	else
-		actor->flags = locvar1;
-	P_SetThingPosition(actor);
+		locvar1 = actor->flags & ~locvar1;
+	if ((locvar1 & (MF_NOBLOCKMAP|MF_NOSECTOR)) != (actor->flags & (MF_NOBLOCKMAP|MF_NOSECTOR))) // Blockmap/sector status has changed, so reset the links
+		unlinkthings = true;
+
+	if (unlinkthings) {
+		P_UnsetThingPosition(actor);
+		if (sector_list)
+		{
+			P_DelSeclist(sector_list);
+			sector_list = NULL;
+		}
+	}
+
+	actor->flags = locvar1;
+
+	if (unlinkthings)
+		P_SetThingPosition(actor);
}
// Function: A_SetObjectFlags2