[BUGFIX] fix hash join close core bug

src/sql/engine/join/hash_join/ob_hj_partition.h

@@ -89,7 +89,9 @@ public:
   }
 
   inline void close() {
-    return partition_store_->close();
+    if (OB_NOT_NULL(partition_store_)) {
+      partition_store_->close();
+    }
   }
 
   inline int rescan() {