fix removing user

abonapp/models.py

@@ -284,6 +284,7 @@ class Abon(BaseAccount):
             raise LogicError(_('NAS required'))
         try:
             agent_abon = self.build_agent_struct()
+            if agent_abon is not None:
                 mngr = self.nas.get_nas_manager()
                 mngr.remove_user(agent_abon)
         except (NasFailedResult, NasNetworkError, ConnectionResetError) as e: