mpegts: handle AVMEDIA_TYPE_UNKNOWN correctly

It is negative, so can't be used for left shifting.

This fixes ubsan runtime error: shift exponent -1 is negative
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavformat/mpegts.c

@@ -2353,7 +2353,8 @@ static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
                 int types = 0;
                 for (i = 0; i < ts->stream->nb_streams; i++) {
                     AVStream *st = ts->stream->streams[i];
-                    types |= 1<<st->codecpar->codec_type;
+                    if (st->codecpar->codec_type >= 0)
+                        types |= 1<<st->codecpar->codec_type;
                 }
                 if ((types & (1<<AVMEDIA_TYPE_AUDIO) && types & (1<<AVMEDIA_TYPE_VIDEO)) || pos > 100000) {
                     av_log(ts->stream, AV_LOG_DEBUG, "All programs have pmt, headers found\n");