[jitsi] black screen and stale pending call when prematurely ending the call

Steps to reproduce: Join Jitsi call -> end the call before it's joined -> the call view controller become black and cannot end the call. See https://matrix.to/#/!tDRGDwZwQnlkowsjsm:matrix.org/$15113266722207364bdqju:matrix.org

Start by reproducing the Jitsi flow: join a call, end it before joining completes, and observe the black call view and stale pending call. Trace the call view controller and pending-call cleanup involved in that flow. Done means prematurely ending the call leaves no stale pending call and the view remains usable.

Written by the indexing model from the issue text.