avformat/flvdec: Free metaVideoColor

Fixes: memeleak
Fixes: 70659/clusterfuzz-testcase-minimized-ffmpeg_dem_KUX_fuzzer-4539872627458048

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

libavformat/flvdec.c

@@ -1111,6 +1111,7 @@ static int flv_parse_video_color_info(AVFormatContext *s, AVStream *st, int64_t
         return TYPE_UNKNOWN;
     }
 
+    av_free(flv->metaVideoColor);
     if (!(flv->metaVideoColor = av_mallocz(sizeof(FLVMetaVideoColor)))) {
         return AVERROR(ENOMEM);
     }