SQL function does not return a value

SELECT 
  n.nspname AS func_schema, 
  pr.proname AS func_name, 
   pg_get_function_identity_arguments(pr.oid) AS parameters,
  regexp_replace(pg_get_functiondef(pr.oid),'[\r\n]','<br>','g')  AS func_src
FROM 
  pg_catalog.pg_proc pr, 
  pg_catalog.pg_namespace n,
  pg_catalog.pg_language l,
  pg_catalog.pg_type t
WHERE 
  pr.pronamespace = n.oid 
  AND pr.prolang=l.oid 
  AND pr.prorettype=t.oid 
  AND pr.prokind='f' 
  AND l.lanname='sql' 
  AND t.typname='void' 
  AND pg_get_functiondef(pr.oid)~*'RETURNING[[:space:]]' 
AND n.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
ORDER BY func_schema, func_name, parameters;