mpegts: fix handling of files smaller than 8kb

Fixes Ticket1094

Analyzed-by: mjs973
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegts.c

@@ -1929,16 +1929,14 @@ static int mpegts_read_header(AVFormatContext *s)
 {
     MpegTSContext *ts = s->priv_data;
     AVIOContext *pb = s->pb;
-    uint8_t buf[8*1024];
+    uint8_t buf[8*1024]={0};
     int len;
     int64_t pos;
 
     /* read the first 8192 bytes to get packet size */
     pos = avio_tell(pb);
     len = avio_read(pb, buf, sizeof(buf));
-    if (len != sizeof(buf))
-        goto fail;
-    ts->raw_packet_size = get_packet_size(buf, sizeof(buf));
+    ts->raw_packet_size = get_packet_size(buf, len);
     if (ts->raw_packet_size <= 0) {
         av_log(s, AV_LOG_WARNING, "Could not detect TS packet size, defaulting to non-FEC/DVHS\n");
         ts->raw_packet_size = TS_PACKET_SIZE;