Error doing job: Task exception was never retrieved (v0.65.5)

Configuration
1

No idea what may be causing these persistent errors. Running Home Assistant 0.65.5

Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/asyncio/tasks.py", line 180, in _step
    result = coro.send(None)
  File "/usr/src/app/homeassistant/components/device_tracker/__init__.py", line 313, in async_see
    hide_if_away=self.defaults.get(CONF_AWAY_HIDE, DEFAULT_AWAY_HIDE))
AttributeError: 'NoneType' object has no attribute 'get'

My device_tracker configuration is as follows…

device_tracker:
  - platform: asuswrt
    host: 192.168.1.1
    username: admin
    password: !secret asus_passwd
    new_device_defaults:
    track_new_devices: False
    hide_if_away: False
  - platform: owntracks
    max_gps_accuracy: 200