Fixed an issue where mobs instantly walked after being spotted (#7738)

* Fixed an issue where mobs instantly walked after being spotted
  MIN_RANDOMWALKTIME was initialized too early
* This behavior is only applied on the monster script command

src/map/mob.cpp

@@ -1571,6 +1571,12 @@ int mob_randomwalk(struct mob_data *md,t_tick tick)
 
 	nullpo_ret(md);
 
+	// Initialize next_walktime
+	if (md->next_walktime == INVALID_TIMER) {
+		md->next_walktime = tick+rnd()%1000+MIN_RANDOMWALKTIME;
+		return 1;
+	}
+
 	if(DIFF_TICK(md->next_walktime,tick)>0 ||
 	   status_has_mode(&md->status,MD_NORANDOMWALK) ||
 	   !unit_can_move(&md->bl) ||

src/map/script.cpp

@@ -11157,11 +11157,18 @@ BUILDIN_FUNC(monster)
 	else
 		m = map_mapname2mapid(mapn);
 
+	TBL_MOB* md;
+
 	for(i = 0; i < amount; i++) { //not optimised
 		int mobid = mob_once_spawn(sd, m, x, y, str, class_, 1, event, size, ai);
 
-		if (mobid)
+		if (mobid > 0) {
+			md = map_id2md(mobid);
+			if (md)
+				md->next_walktime = INVALID_TIMER;
+
 			mapreg_setreg(reference_uid(add_str("$@mobid"), i), mobid);
+		}
 	}
 
 	return SCRIPT_CMD_SUCCESS;
@@ -11274,11 +11281,18 @@ BUILDIN_FUNC(areamonster)
 	else
 		m = map_mapname2mapid(mapn);
 
+	TBL_MOB* md;
+
 	for(i = 0; i < amount; i++) { //not optimised
 		int mobid = mob_once_spawn_area(sd, m, x0, y0, x1, y1, str, class_, 1, event, size, ai);
 
-		if (mobid)
+		if (mobid > 0) {
+			md = map_id2md(mobid);
+			if (md)
+				md->next_walktime = INVALID_TIMER;
+
 			mapreg_setreg(reference_uid(add_str("$@mobid"), i), mobid);
+		}
 	}
 
 	return SCRIPT_CMD_SUCCESS;