[CP][BUGFIX] add fix zero lob val

src/storage/lob/ob_lob_manager.cpp

@@ -25,6 +25,8 @@ namespace oceanbase
 namespace storage
 {
 
+const ObLobCommon ObLobManager::ZERO_LOB = ObLobCommon();
+
 int ObLobManager::mtl_new(ObLobManager *&m) {
   int ret = OB_SUCCESS;
   const uint64_t tenant_id = MTL_ID();