Fixes: memleaks
Fixes: 18855/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAVOICE_fuzzer-5687647317524480

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>