Fix Typo in Cleans up Summoner dual-cast attacks commit (Map Crash Issue) (#4677)

* Fixes #4676.
*  Fixes a typo in Professor’s Dual Casting check.
Thanks to @reunite-ro!

src/map/skill.cpp

@@ -3763,7 +3763,7 @@ int64 skill_attack (int attack_type, struct block_list* src, struct block_list *
 			case MG_COLDBOLT:
 			case MG_FIREBOLT:
 			case MG_LIGHTNINGBOLT:
-				if (sc && sc->data[SC_DOUBLECAST] && rnd() % 100 < tsc->data[SC_DOUBLECAST]->val2)
+				if (sc && sc->data[SC_DOUBLECAST] && rnd() % 100 < sc->data[SC_DOUBLECAST]->val2)
 					//skill_addtimerskill(src, tick + dmg.div_*dmg.amotion, bl->id, 0, 0, skill_id, skill_lv, BF_MAGIC, flag|2);
 					skill_addtimerskill(src, tick + dmg.amotion, bl->id, 0, 0, skill_id, skill_lv, BF_MAGIC, flag|2);
 				break;