Added a map cell check for Shadow Leap (fixes #1291)

* Resolves players being able to enter non-walkable parts of maps.
Thanks to @Tokeiburu!

src/map/skill.c

@@ -11712,7 +11712,7 @@ int skill_castend_pos2(struct block_list* src, int x, int y, uint16 skill_id, ui
 		}
 		break;
 	case NJ_SHADOWJUMP:
-		if( skill_check_unit_movepos(3, src, x, y, 1, 0) ) //You don't move on GVG grounds.
+		if( map_getcell(src->m,x,y,CELL_CHKREACH) && skill_check_unit_movepos(3, src, x, y, 1, 0) ) //You don't move on GVG grounds.
 			clif_blown(src);
 		status_change_end(src, SC_HIDING, INVALID_TIMER);
 		break;