Lovelace: Error when showing a card with unavailable entity

@gregg098 commented on Sep 4, 2018, 6:47 PM UTC:

Home Assistant release with the issue:

0.77.3

Last working Home Assistant release (if known):
Unknown if it ever worked.

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

Ubuntu Server 16.04 - Docker CE 18.06-1
Using the latest docker image

Component/platform:

https://www.home-assistant.io/lovelace/entities/

Description of problem:
For this particular issue, I am using the Google Cast integration. In my front end (LoveLace), I added an entities card with a number of media players.

This works as expected, except when the TV is turned off, the Chromecast attached goes away since it is plugged directly into the TV's USB port. The device will not show on the list (expected), but every time I navigate to that page, a bubble at the bottom of the page pops up saying:
Service system_log/write called.

Then, an error is added to the logs each time:
2018-09-04 11:33:42 ERROR (MainThread) [frontend.js.latest.201809030] https://<domain>/frontend_latest/app-1fe7ad4f.js:434:176 Uncaught TypeError: Cannot read property '_stateDisplay' of null

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

      - type: entities
        title: Media
        entities:
          - remote.upstairs
          - media_player.roku_2_upstairs
          - media_player.upstairs_tv
          - media_player.upstairs_home
          - media_player.upstairs_group
          - media_player.whole_house

Note: There are other similar blocks in my config that have the same result. For this instance, the entity media_player.upstairs_tv is the problem.

Traceback (if applicable):

2018-09-04 11:33:42 ERROR (MainThread) [frontend.js.latest.201809030] https://<domain>/frontend_latest/app-1fe7ad4f.js:434:176 Uncaught TypeError: Cannot read property '_stateDisplay' of null

Additional information:
I also attempted to work around this issue by using a conditional card that only displays the entity if the device tracker (Unifi) shows the device as "home." The error still displays even though the condition is not met to display the card. This is not ideal anyways since I can't lump conditionals in with an entity card. It would have to be something like a vertical stack for this to work.

This issue was moved by jeradM from home-assistant/home-assistant#16423.

@arsaboo commented on Sep 4, 2018, 9:45 PM UTC:

While this is the expected behavior (in that, unavailable entities used in LL will result in that error), I agree that many times the entity may be temporarily unavailable. LL should handle such cases gracefully.

[balloob]

Yeah, we should show a row with unavailable, not throw errors.