avformat/mpegts: Initialize predefined_SLConfigDescriptor_seen

Fixes: use of uninitialized variable
Fixes: 368729566/clusterfuzz-testcase-minimized-ffmpeg_dem_MPEGTS_fuzzer-6044501804646400

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit db7b4fc89f)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mpegts.c

@@ -1672,6 +1672,8 @@ static int mp4_read_iods(AVFormatContext *s, const uint8_t *buf, unsigned size,
     MP4DescrParseContext d;
     int ret;
 
+    d.predefined_SLConfigDescriptor_seen = 0;
+
     ret = init_MP4DescrParseContext(&d, s, buf, size, descr, max_descr_count);
     if (ret < 0)
         return ret;