end line drawing

def drawing_end(self):
        '''end line drawing'''
        from MAVProxy.modules.mavproxy_map import mp_slipmap
        if self.draw_callback is None:
            return
        self.draw_callback(self.draw_line)
        self.draw_callback = None
        self.map.add_object(mp_slipmap.SlipDefaultPopup(self.default_popup, combine=True))
        self.map.add_object(mp_slipmap.SlipClearLayer('Drawing'))