Picture-In-Picture window doesn't doesn't close when video is deleted

[fcolley]

Have you read the FAQ and checked for duplicate open issues?
Yes

What version of Shaka Player are you using?
Build: Shaka v2.5.3-master-38-gfd326951 (uncompiled)

Can you reproduce the issue with our latest release version?
Yes

Can you reproduce the issue with the latest code from master?
Yes

Are you using the demo app or your own custom app?
Shaka Player Demo

What browser and OS are you using?
Environment: Linux, Mac, Win10, etc

What did you do?
Steps:

1. Navigate to: https://nightly-dot-shaka-player-demo.appspot.com
2. Download video asset and select Play when it's finished (we used Angel One)
3. Select the Overflow menu and Picture-In-Picture
4. Delete the downloaded content while you are still playing it in Picture-In-Picture

Actual Result:
The video pauses but the PIP window remains open and frozen on the last frame played

Expected:
When the video is no longer available it's expected that the player would close
(This is how it works when not in PIP mode)