Chrome Version: 72.0.3599.0
OS: macOS 10.14

What steps will reproduce the problem?
(1) Open the Harmony cast dialog (chrome://flags/#views-cast-dialog)
(2) Create a meeting on your Google calendar and cast to it (issue 901333 workaround).
(3) Join the meeting normally in another tab/window/browser.
(4) From the other tab/window/browser, remove the participant representing the casted tab from the meeting. (A Cast warning icon should appear to the right of the omnibox.)
(5) Delete the meeting from your calendar.
(6) Wait a moment and click the error button.

More realistically (though I can't reproduce this right now), I've seen cast go into the same error state when a meeting ends and everyone else leaves (something about not enough other participants?). The meeting is over on my calendar, so it no longer appears in the list and I can't dismiss the error.

What is the expected result?
There's some way to dismiss the error state.

What happens instead?
There is no way to dismiss the error state, it persists until I relaunch Chrome.