avcodec/vlc: free multi on fail

Fixes: leak
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_UTVIDEO_fuzzer-6449246523752448

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

libavcodec/vlc.c

@@ -481,6 +481,7 @@ int ff_vlc_init_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int
 fail:
     if (buf != localbuf)
         av_free(buf);
+    ff_vlc_free_multi(multi);
     return AVERROR_INVALIDDATA;
 }