core: TPLink component fails to register devices outside of current subnet (discovery & declared)

Home Assistant release with the issue:

0.89.1

Last working Home Assistant release (if known): 0.88

Operating environment (Hass.io/Docker/Windows/etc.):

Docker, Hassio Tested Component/platform:

https://www.home-assistant.io/components/tplink/

Description of problem: I host all my TPLink IoT devices on a separate subnet/vlan for security purposes and up until 0.89 (the addition of the dedicated TPLink component vs switch/light components). The devices still work in the Kasa app but are unable to connect given the new component. Devices on the same subnet as hass work properly.

Note: The hass instance is running on the 10.0.1.x subnet and my IOT/TP-Link devices are on 10.0.8.x

Problem-relevant configuration.yaml entries and (fill out even if it seems unimportant):

tplink:
  discovery: true
  light:
    - host: 10.0.8.252

Traceback (if applicable):

2019-03-10 21:55:27 ERROR (MainThread) [homeassistant.core] Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/src/app/homeassistant/helpers/entity_platform.py", line 257, in _async_add_entity
    if entity.unique_id is not None:
  File "/usr/src/app/homeassistant/components/tplink/light.py", line 82, in unique_id
    return self._sysinfo["mac"]
TypeError: 'NoneType' object is not subscriptable

Additional information: I have also tested this with switches and neither are working as expected and throw the same error.

This is a refresh of this issue that started to get off-topic.