backport: fix(signaling): keep the participant limit screen visible and survive unknown messages

Maximilian Fußrequested to merge
m.fuss/web-app:3547-backport-keep-the-participant-limit-screen-visible-and-survive-unknown-messages-to-v2-9-x into release/v2.9.x

fix(signaling): keep the participant limit screen visible and survive unknown messages

Closes #3547 (closed)

(cherry picked from commit ce994df7)

Merge request reports