10l, add check forgotten in last commit

Originally committed as revision 10442 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/nuv.c

@@ -158,6 +158,10 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     if (c->codec_frameheader) {
         get_quant_quality(c, buf[10]);
         rtjpeg_decode_init(&c->rtj, &c->dsp, c->width, c->height, c->lq, c->cq);
+        if (buf_size < 12) {
+            av_log(avctx, AV_LOG_ERROR, "invalid nuv video frame\n");
+            return -1;
+        }
         buf = &buf[12];
         buf_size -= 12;
     }