Cannot leave an Alliance

When you click "Leave Alliance", it will occur:
SQL/DB Error -- [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 'AND username != ''' at line 1]

Are you sure you want to leave ? Yes/No




After you click yes, it will occur:
SQL/DB Error -- [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 '' at line 1]

You are no longer a member of .




However, when you click back to alliance section, you are still a member of previous alliance.