incase None > int in python3

Author: Huibean

dronekit/__init__.py

@@ -1775,7 +1775,7 @@ def is_armable(self):
         # check that mode is not INITIALSING
         # check that we have a GPS fix
         # check that EKF pre-arm is complete
-        return self.mode != 'INITIALISING' and self.gps_0.fix_type > 1 and self._ekf_predposhorizabs
+        return self.mode != 'INITIALISING' and (self.gps_0.fix_type is not None and self.gps_0.fix_type > 1) and self._ekf_predposhorizabs
 
     @property
     def system_status(self):