avcodec/msrledec: Ask for sample that uses a branch with a unused byte

Finding out if this is correct or buggy is easiest with a sample

Fixes: CID1297620
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/msrledec.c

@@ -63,6 +63,7 @@ static int msrle_decode_pal4(AVCodecContext *avctx, AVPicture *pic,
                 stream_byte = bytestream2_get_byte(gb);
                 pixel_ptr += stream_byte;
                 stream_byte = bytestream2_get_byte(gb);
+                avpriv_request_sample(avctx, "Unused stream byte %X", stream_byte);
             } else {
                 // copy pixels from encoded stream
                 odd_pixel =  stream_byte & 1;