Adjust the Hell Inferno dark element check (#5316)

* Adjusts the dark element attack check for Hell Inferno to be a bit more accurate.
Thanks to @attackjom and @Lemongrass3110!

src/map/battle.cpp

@@ -6123,7 +6123,7 @@ struct Damage battle_calc_magic_attack(struct block_list *src,struct block_list
 				s_ele = ELE_HOLY;
 			break;
 		case WL_HELLINFERNO:
-			if (mflag == ELE_DARK) {
+			if (mflag & 2) { // ELE_DARK
 				s_ele = ELE_DARK;
 				ad.div_ = 3;
 			}
@@ -6494,7 +6494,7 @@ struct Damage battle_calc_magic_attack(struct block_list *src,struct block_list
 						break;
 					case WL_HELLINFERNO:
 						skillratio += -100 + 400 * skill_lv;
-						if (mflag == ELE_DARK)
+						if (mflag & 2) // ELE_DARK
 							skillratio += 200;
 						RE_LVL_DMOD(100);
 						break;

src/map/skill.cpp

@@ -5845,7 +5845,7 @@ int skill_castend_damage_id (struct block_list* src, struct block_list *bl, uint
 	case WL_HELLINFERNO:
 		if (flag & 1) {
 			skill_attack(BF_MAGIC, src, src, bl, skill_id, skill_lv, tick, flag);
-			skill_addtimerskill(src, tick + 300, bl->id, 0, 0, skill_id, skill_lv, BF_MAGIC, flag | ELE_DARK);
+			skill_addtimerskill(src, tick + 300, bl->id, 0, 0, skill_id, skill_lv, BF_MAGIC, flag | 2);
 		} else {
 			clif_skill_nodamage(src, bl, skill_id, skill_lv, 1);
 			map_foreachinrange(skill_area_sub, bl, skill_get_splash(skill_id, skill_lv), BL_CHAR, src, skill_id, skill_lv, tick, flag | BCT_ENEMY | SD_SPLASH | 1, skill_castend_damage_id);