Backport of "splitmuxsink: Don't crash on EOS without buffer" into 1.20
Backport of !2174 (merged) "splitmuxsink: Don't crash on EOS without buffer".
Commits:
- b233df35 splitmuxsink: Don't crash on EOS without buffer
- ab459f05 splitmuxsink: Fix memory leak (from !2751 (merged))
Edited by Tim-Philipp Müller