Fixed an issue caused by duel-song interaction

- Fixes #546 (follow-up to 127f9b5)
- Special thanks to kyeme, Mordekaiser

Signed-off-by: Haru <haru@dotalux.com>

src/map/battle.c

@@ -6532,7 +6532,7 @@ int battle_check_target( struct block_list *src, struct block_list *target,int f
 				) {
 					if( t_bl->type == BL_PC && (sd->duel_group == ((TBL_PC*)t_bl)->duel_group) )
 						return (BCT_ENEMY&flag)?1:-1; // Duel targets can ONLY be your enemy, nothing else.
-					else if ( src->type != BL_SKILL || (flag&BCT_ENEMY) )
+					else if (src->type != BL_SKILL || (flag&BCT_ALL) != BCT_ALL)
 						return 0;
 				}
 			}