case 13:
c->pic.key_frame = 0;
c->pic.pict_type = AV_PICTURE_TYPE_P;
+ if (!c->prev.data[0]) {
+ av_log(avctx, AV_LOG_ERROR, "Missing reference frame\n");
+ return AVERROR_INVALIDDATA;
+ }
decode_13(avctx, c, c->pic.data[0], srcptr, c->prev.data[0]);
break;
default: