Fixed ItemCost is invalid when specified level (#6796)

* Fixed #6573.
* Fixes ItemCost being invalid when specifying level.
Thanks to @dimasshotta and @CairoLee!

src/map/skill.cpp

@@ -18224,6 +18224,13 @@ struct s_skill_condition skill_get_requirement(struct map_session_data* sd, uint
 						break;
 					}
 				}
+				else {
+					// Process level_dependent requirement
+					if (level_dependent && skill_lv <= MAX_SKILL_ITEM_REQUIRE) {
+						req.itemid[0] = skill->require.itemid[skill_lv - 1];
+						req.amount[0] = skill->require.amount[skill_lv - 1];
+					}
+				}
 
 				// Check requirement for gemstone.
 				if (itemdb_group.item_exists(IG_GEMSTONE, req.itemid[i])) {