NoneType not callable error when updating config options

[mjmeli]

Error when updating configuration options, intermittent

Logger: homeassistant
Source: custom_components/duke_energy_gateway/coordinator.py:133
Integration: Duke Energy Gateway (documentation, issues)
First occurred: 9:23:53 AM (1 occurrences)
Last logged: 9:23:53 AM

Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/config/custom_components/duke_energy_gateway/__init__.py", line 119, in async_reload_entry
    await async_unload_entry(hass, entry)
  File "/config/custom_components/duke_energy_gateway/__init__.py", line 112, in async_unload_entry
    coordinator.async_realtime_unsubscribe_all_from_dispatcher()
  File "/config/custom_components/duke_energy_gateway/coordinator.py", line 140, in async_realtime_unsubscribe_all_from_dispatcher
    self.async_realtime_unsubscribe_from_dispatcher(source)
  File "/config/custom_components/duke_energy_gateway/coordinator.py", line 133, in async_realtime_unsubscribe_from_dispatcher
    self.async_realtime_remove_subscriber_funcs_by_source[source]()
TypeError: 'NoneType' object is not callable