Backport of "qtdemux: Avoid crash on reconfiguring." into 1.20
Backport of !2869 (merged) "qtdemux: Avoid crash on reconfiguring.".
Commits:
- c2fa0b50 qtdemux: Avoid crash on reconfiguring.
Backport of !2869 (merged) "qtdemux: Avoid crash on reconfiguring.".
Commits: