With some of the preceding commits in the "multiplying remote
thumbnails" story line, I started hitting this error with 100%
reproducibility:

1. Have a remote participant prepared in conferenceA. Web will do as
well.
2. On iOS prepare to join conferenceB in Safari and use the same device
for step 3.
3. Join conferenceA on the iOS device from step 2 with audio-only. The
audio-only is so that avatars are always visible. Wait for the remote
participant prepared in step 1 to appear.
4. Switch to Safari and hit "Continue in the app" to have the app leave
conferenceA and join conferenceB.

What happens:
After the iOS device joins conferenceB in the Jitsi Meet app, the local
participant is on the large video (as expected) but the avatar of the
local participant is the default audo-generated auto-colored
placeholder. That's because this error was hit and the avatar couldn't
be "fetched".