crashes when all laser scan data is out of range

[cypressf]

Traceback (most recent call last):
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 656, in
main(sys.argv)
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 649, in main
rescuebot.run()
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 621, in run
cmd_vel = self.get_cmd_vel()
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 473, in follow_wall
angular_velocity = self.follow_wall_helper(self.lead_right_avg, self.trailing_right_avg, 'right')
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 486, in follow_wall_helper
point_to_wall = self.get_point_to_wall()
File "/home/cypressf/catkin_ws/src/rescuebot/scripts/runner.py", line 517, in get_point_to_wall
closest_point = min(self.filtered_points)
ValueError: min() arg is an empty sequence