Fixes Magnetic field behavior (#5423)

* Fixes #5401.
* Minor optimizations to core skill behavior.
* Adjusts the status timer to be stored in val4.
* Impose a unit lock before doing status damage.
* Check for status state before attempting to reapply the status timer.
Thanks to @LotusRO!

src/map/skill.cpp

@@ -5913,10 +5913,6 @@ int skill_castend_damage_id (struct block_list* src, struct block_list *bl, uint
 			map_foreachinallrange(skill_area_sub, bl, skill_get_splash(skill_id, skill_lv), splash_target(src), src, skill_id, skill_lv, tick, flag|BCT_ENEMY|SD_SPLASH|1, skill_castend_damage_id);
 		}
 		break;
-
-	case NC_MAGNETICFIELD:
-		sc_start2(src,bl,SC_MAGNETICFIELD,100,skill_lv,src->id,skill_get_time(skill_id,skill_lv));
-		break;
 	case SC_FATALMENACE:
 		if( flag&1 )
 			skill_attack(BF_WEAPON,src,src,bl,skill_id,skill_lv,tick,flag);
@@ -10227,10 +10223,14 @@ int skill_castend_nodamage_id (struct block_list *src, struct block_list *bl, ui
 		break;
 
 	case NC_MAGNETICFIELD:
-		clif_skill_damage(src,bl,tick,status_get_amotion(src),0,-30000,1,skill_id,skill_lv,DMG_SINGLE);
-		if (map_flag_vs(src->m)) // Doesn't affect the caster in non-PVP maps [exneval]
-			sc_start2(src,bl,type,100,skill_lv,src->id,skill_get_time(skill_id,skill_lv));
-		map_foreachinallrange(skill_area_sub,bl,skill_get_splash(skill_id,skill_lv),splash_target(src),src,skill_id,skill_lv,tick,flag|BCT_ENEMY|SD_SPLASH|1,skill_castend_damage_id);
+		if (flag & 1) {
+			sc_start2(src, bl, SC_MAGNETICFIELD, 100, skill_lv, src->id, skill_get_time(skill_id, skill_lv));
+		} else {
+			if (map_flag_vs(src->m)) // Doesn't affect the caster in non-PVP maps [exneval]
+				sc_start2(src, bl, type, 100, skill_lv, src->id, skill_get_time(skill_id, skill_lv));
+			map_foreachinallrange(skill_area_sub, bl, skill_get_splash(skill_id, skill_lv), splash_target(src), src, skill_id, skill_lv, tick, flag | BCT_ENEMY | SD_SPLASH | 1, skill_castend_nodamage_id);
+			clif_skill_damage(src, bl, tick, status_get_amotion(src), 0, -30000, 1, skill_id, skill_lv, DMG_SINGLE);
+		}
 		break;
 
 	case NC_REPAIR:

src/map/status.cpp

@@ -11564,8 +11564,8 @@ int status_change_start(struct block_list* src, struct block_list* bl,enum sc_ty
 			tick_time = 5000; // [GodLesZ] tick time
 			break;
 		case SC_MAGNETICFIELD:
-			val3 = tick / 1000;
 			tick_time = 1000; // [GodLesZ] tick time
+			val4 = tick / tick_time;
 			break;
 		case SC_INSPIRATION:
 			val2 = (sd?sd->status.job_level:50);
@@ -14510,14 +14510,17 @@ TIMER_FUNC(status_change_timer){
 		break;
 
 	case SC_MAGNETICFIELD:
-		if (--(sce->val3) >= 0) {
+		if (--(sce->val4) >= 0) {
 			struct block_list *src = map_id2bl(sce->val2);
 
 			if (!src || (src && (status_isdead(src) || src->m != bl->m)))
 				break;
+			map_freeblock_lock();
 			if (!status_charge(bl, 0, 50))
 				status_zap(bl, 0, status->sp);
-			sc_timer_next(1000 + tick);
+			if (sc->data[type])
+				sc_timer_next(1000 + tick);
+			map_freeblock_unlock();
 			return 0;
 		}
 		break;