Guard browsing Spotify if setup failed

[jjlawren]

Proposed change

If Spotify is configured but hasn't successfully loaded it can lead to errors when browsing from another integration (e.g., Sonos).

File "/usr/src/homeassistant/homeassistant/components/sonos/media_player.py", line 698, in async_browse_media
    return await media_browser.async_browse_media(
File "/usr/src/homeassistant/homeassistant/components/sonos/media_browser.py", line 109, in async_browse_media
    return await spotify.async_browse_media(hass, None, None, can_play_artist=False)
File "/usr/src/homeassistant/homeassistant/components/spotify/__init__.py", line 63, in async_browse_media
    info = list(hass.data[DOMAIN].values())[0]
KeyError: 'spotify'

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

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• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
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• Tests have been added to verify that the new code works.

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[probot-home-assistant]

Hey there @frenck, mind taking a look at this pull request as it has been labeled with an integration (spotify) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[balloob]

Should we catch this inside Sonos?

[frenck]

I think this makes a lot of sense to do here, mainly because anything else can just use it without having to worry about it.

[balloob]

Sorry, I meant catch BrowseError in Sonos. The check here is indeed correct.

[jjlawren]

I don't think that's necessary. It should only hit this codepath if the browser is explicitly trying to browse into Spotify. It'll only hit this at the root level is Spotify is the only source available.