[FIX] b_shift: Exemption wizard

beesdoo_shift/wizard/temporary_exemption.py

@@ -11,9 +11,9 @@ class TemporaryExemption(models.TransientModel):
 
     @api.multi
     def exempt(self):
-        self = self._check() #maybe a different group
+        self = self._check()  # maybe a different group
         status_id = self.env['cooperative.status'].search([('cooperator_id', '=', self.cooperator_id.id)])
-        if status_id.temporary_exempt_end_date >= status_id.today:
+        if status_id.temporary_exempt_end_date and status_id.temporary_exempt_end_date >= status_id.today:
             raise ValidationError(_("You cannot encode new temporary exemptuon since the previous one are not over yet"))
         status_id.sudo().write({
             'temporary_exempt_start_date': self.temporary_exempt_start_date,