mpegts: fix stack array overread in read_sl_header()

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegts.c

@@ -1822,7 +1822,7 @@ static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size)
 static int handle_packets(MpegTSContext *ts, int nb_packets)
 {
     AVFormatContext *s = ts->stream;
-    uint8_t packet[TS_PACKET_SIZE];
+    uint8_t packet[TS_PACKET_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
     int packet_num, ret = 0;
 
     if (avio_tell(s->pb) != ts->last_pos) {