avcodec/wmaprodec: Set packet_loss when we error out on a sanity check

Fixes: left shift of negative value -34
Fixes: 18719/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAPRO_fuzzer-5642658173419520

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/wmaprodec.c

@@ -1644,6 +1644,7 @@ static int decode_packet(AVCodecContext *avctx, WMAProDecodeCtx *s,
         if (avctx->codec_id == AV_CODEC_ID_WMAPRO && buf_size < avctx->block_align) {
             av_log(avctx, AV_LOG_ERROR, "Input packet too small (%d < %d)\n",
                    buf_size, avctx->block_align);
+            s->packet_loss = 1;
             return AVERROR_INVALIDDATA;
         }