Spurious error "query has no destination for result data" for PL/pgSQL function \"xata.pg_catalog\".pg_database_size(name)

[emarsden]

Using the xata.io free tier, the following query

SELECT
   pg_catalog.pg_total_relation_size(c.oid),
   obj_description(c.oid, 'pg_class')
FROM pg_class c
JOIN pg_namespace n ON c.relnamespace = n.oid
WHERE (n.nspname, c.relname) = ($1, $2)

as a prepared statement with an existing schema name and table name triggers the following (spurious) error:

query has no destination for result data (where: PL/pgSQL function \"xata.pg_catalog\".pg_database_size(name) line 3 at SQL statement, routine: exec_stmt_execsql, line: 4442, file: pl_exec.c, hint: If you want to discard the results of a SELECT, use PERFORM instead.)

The query works fine with standard PostgreSQL.