Backport of "libav: Fix for APNG encoder property registration" into 1.20
Backport of !2724 (merged) "libav: Fix for APNG encoder property registration".
Commits:
- 0513e517 libav: Fix for APNG encoder property registration
Backport of !2724 (merged) "libav: Fix for APNG encoder property registration".
Commits: