ERROR: operator does not exist: ag_catalog.agtype + ag_catalog.agtype

I am getting an error when I ran the below queries in PostgreSQL-11:

```
SELECT * FROM ag_catalog.cypher('graph_path', $$ CREATE (:L {a: 1, b: 2, c: 3}), (:L {a: 2, b: 3, c: 1}), (:L {a: 3, b: 1, c: 2}) $$) as (a ag_catalog.agtype);

SELECT * FROM ag_catalog.cypher('graph_path', $$ MATCH (x:L) RETURN (x.a + x.b + x.c) + count(*) + count(*), x.a + x.b + x.c $$) as (count ag_catalog.agtype, key ag_catalog.agtype);
```

**ERROR: operator does not exist: ag_catalog.agtype + ag_catalog.agtype
LINE 1: ...her('graph_path', $$ MATCH (x:L) RETURN (x.a + x.b + x....
                                                                                                  ^
HINT: No operator matches the given name and argument types. You might need to add explicit type casts.**