Submit .sig error

[Cross]

When trying to add a .sig to our forum users get this error:

Could not update user table

DEBUG MODE

SQL Error : 1064 You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE user_id = 3' at line 3

UPDATE phpbb_users SET WHERE user_id = 3

Line : 444
File : profilcp_profil_signature.php

Any help is appreciated as to a solution.