mts: FindPmt checks validity of data length

stream/mts/mpegts.go

@@ -130,6 +130,9 @@ type Packet struct {
 // FindPMT will take a clip of mpegts and try to find a PMT table - if one
 // is found, then it is returned, otherwise nil and an error is returned.
 func FindPMT(d []byte) (p []byte, err error) {
+	if len(d) < mpegTsSize {
+		return nil, errors.New("Mmpegts data not of valid length")
+	}
 	for i := 0; i < len(d); i += mpegTsSize {
 		pid := (uint16(d[i+1]&0x1f) << 8) | uint16(d[i+2])
 		if pid == pmtPid {