Incorrect usage of DB GRANT and NON-DB PRIVILEGES

[morgo]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create user u1;
GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u1`; -- user exists
GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u2`; 

2. What did you expect to see? (Required)

mysql [localhost:8028] {root} (test) > GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u1`;
Query OK, 0 rows affected (0.00 sec)

mysql [localhost:8028] {root} (test) > GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u2`;
ERROR 1410 (42000): You are not allowed to create a user with GRANT

3. What did you see instead (Required)

tidb> create user u1;
Query OK, 0 rows affected (0.01 sec)

tidb> GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u1`; -- user exists
ERROR 1221 (HY000): Incorrect usage of DB GRANT and NON-DB PRIVILEGES
tidb> GRANT CREATE TEMPORARY TABLES,DELETE,EXECUTE,INSERT,SELECT,SHOW VIEW,TRIGGER,UPDATE ON `test`.* TO `u2`; 
ERROR 1105 (HY000): runtime error: invalid memory address or nil pointer dereference

4. What is your TiDB version? (Required)

tidb> SELECT tidb_version()\G
*************************** 1. row ***************************
tidb_version(): Release Version: v5.5.0-alpha-406-g67789193d-dirty
Edition: Community
Git Commit Hash: 67789193da312967f486ae51fb85787446c3fd53
Git Branch: remove-memory-vars
UTC Build Time: 2022-03-02 01:07:22
GoVersion: go1.16.9
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false
1 row in set (0.00 sec)