scpr: Added missing error check

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavcodec/scpr.c

@@ -582,6 +582,8 @@ static int decompress_p(AVCodecContext *avctx,
 
                 for (; by < y * 16 + sy2 && by < avctx->height;) {
                     ret = decode_value(s, s->op_model[ptype], 6, 1000, &ptype);
+                    if (ret < 0)
+                        return ret;
                     if (ptype == 0) {
                         ret = decode_unit(s, &s->pixel_model[0][cx + cx1], 400, &r);
                         if (ret < 0)