manager couldn't approve leave despite of having leave request rights

[Marwan]

we have installed the module HR Holiday Extension . we were aiming to restrict the leave approval to direct manager or/and HR officer . the default open ERP installation doesn't allow leave approval for any employee other than HR officer which forced us to define all managers as HR officer . after the installation of HR Holiday Extension , we have added the responsibility of approve leave to all managers and it worked well that the manager become able to view his subordinates leave requests . the aroused problem is that once the manager click approve or Refuse to the leave request , the attached bug appears . we have reviewed all the settings but couldn't identify what are missing to allow the confirmation of approval or refusal of the leave request . your quick response is highly appreciated