Fix a bug that causes worker_create_or_alter_role to crash with NULL input

(cherry picked from commit a7e4d6c94a)

src/backend/distributed/utils/role.c

@@ -73,6 +73,11 @@ alter_role_if_exists(PG_FUNCTION_ARGS)
 Datum
 worker_create_or_alter_role(PG_FUNCTION_ARGS)
 {
+	if (PG_ARGISNULL(0))
+	{
+		ereport(ERROR, (errmsg("role name cannot be NULL")));
+	}
+
 	text *rolenameText = PG_GETARG_TEXT_P(0);
 	const char *rolename = text_to_cstring(rolenameText);
 

src/test/regress/expected/multi_utilities.out

@@ -364,6 +364,11 @@ SELECT worker_hash('(1, 2)'::test_composite_type);
 
 SELECT citus_truncate_trigger();
 ERROR:  must be called as trigger
+-- make sure worker_create_or_alter_role does not crash with NULL input
+SELECT worker_create_or_alter_role(NULL, NULL, NULL);
+ERROR:  role name cannot be NULL
+SELECT worker_create_or_alter_role(NULL, 'create role dontcrash', NULL);
+ERROR:  role name cannot be NULL
 -- confirm that citus_create_restore_point works
 SELECT 1 FROM citus_create_restore_point('regression-test');
 NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');

src/test/regress/sql/multi_utilities.sql

@@ -202,5 +202,9 @@ SELECT worker_hash('(1, 2)'::test_composite_type);
 
 SELECT citus_truncate_trigger();
 
+-- make sure worker_create_or_alter_role does not crash with NULL input
+SELECT worker_create_or_alter_role(NULL, NULL, NULL);
+SELECT worker_create_or_alter_role(NULL, 'create role dontcrash', NULL);
+
 -- confirm that citus_create_restore_point works
 SELECT 1 FROM citus_create_restore_point('regression-test');