avcodec/magicyuv: Free previous VLC table

Fixes: memleak
Fixes: 26788/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MAGICYUV_fuzzer-5184116808744960

Regression since: 1bf30a1beb

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

libavcodec/magicyuv.c

@@ -89,6 +89,7 @@ static int huff_build(HuffEntry he[], uint16_t codes_count[33],
         he[i].code = codes_count[he[i].len];
         codes_count[he[i].len]++;
     }
+    ff_free_vlc(vlc);
     return init_vlc(vlc, FFMIN(max, 12), nb_elems,
                     &he[0].len,  sizeof(he[0]), sizeof(he[0].len),
                     &he[0].code, sizeof(he[0]), sizeof(he[0].code), 0);