TypeError: object of type 'NoneType' has no len()

[patrickpoirier51]

api start /home/patrick/visnav/PrecisionLand.py
GUIDED> Connecting to vehicle...
Vehicle connected!
Running Precision_Land
Using simulator
Frame 0
Exception in APIThread-1: object of type 'NoneType' has no len()
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/droneapi/module/api.py", line 329, in run
self.fn()
File "/usr/local/lib/python2.7/dist-packages/droneapi/module/api.py", line 600, in
APIThread(self, lambda: execfile(args[1], g), args[1])
File "/home/patrick/visnav/PrecisionLand.py", line 248, in
strat.run()
File "/home/patrick/visnav/PrecisionLand.py", line 208, in run
VN_logger.text(VN_logger.DEBUG, 'Rings detected: {0}'.format(len(results[4])))
TypeError: object of type 'NoneType' has no len()

[patrickpoirier51]

changed line 208 to this:
VN_logger.text(VN_logger.DEBUG, 'Rings detected: {0}'.format(results[4]))

[patrickpoirier51]

still got this error when frame is detected:
File "/home/patrick/visnav/PrecisionLand.py", line 192, in run
imageQueue.remove(f)
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()