h265_metadata: Correct error check

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/h265_metadata_bsf.c

@@ -395,7 +395,7 @@ static int h265_metadata_filter(AVBSFContext *bsf, AVPacket *pkt)
 
             err = ff_cbs_insert_unit_content(ctx->cbc, au,
                                              0, HEVC_NAL_AUD, aud, NULL);
-            if (err) {
+            if (err < 0) {
                 av_log(bsf, AV_LOG_ERROR, "Failed to insert AUD.\n");
                 goto fail;
             }