Corrected Hell Inferno Dark damage behavior

* Follow up to dc2c51c.
* Fixes #2623.
* Resolved the Dark damage not being flagged properly.
Thanks to @Sweet520 and @hartonox!

src/map/battle.cpp

@@ -5672,7 +5672,7 @@ struct Damage battle_calc_magic_attack(struct block_list *src,struct block_list
 				s_ele = ELE_HOLY;
 			break;
 		case WL_HELLINFERNO:
-			if (ad.miscflag&ELE_DARK)
+			if (mflag&ELE_DARK)
 				s_ele = ELE_DARK;
 			break;
 		case SO_PSYCHIC_WAVE: