Fixes: memleaks
Fixes: 23306/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5635436931448832

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 9b5fc789fb52af8769ec66e634ea362a67cb5d06)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>