Granting a db level privilege to a non-existent table should not report ErrTableNotExists

[djshow832]

Bug Report

Please answer these questions before submitting your issue. Thanks!

This is introduced by #29273

1. Minimal reproduce step (Required)

mysql> drop table tmpdb.t;
Query OK, 0 rows affected (0.01 sec)

mysql> grant create temporary tables on tmpdb.tmpdb to test_user;
ERROR 1146 (42S02): Table 'tmpdb.tmpdb' doesn't exist

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

mysql> grant create temporary tables on tmpdb.t to test_user;
ERROR 1144 (42000): Illegal GRANT/REVOKE command; please consult the manual to see which privileges can be used

3. What did you see instead (Required)

mysql> grant create temporary tables on tmpdb.tmpdb to test_user;
ERROR 1146 (42S02): Table 'tmpdb.tmpdb' doesn't exist

4. What is your TiDB version? (Required)

master

[unconsolable]

/assign

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.