avcodec/h264_metadata_bsf: Don't use unitialized value

Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/h264_metadata_bsf.c

@@ -528,7 +528,7 @@ static int h264_metadata_update_fragment(AVBSFContext *bsf, AVPacket *pkt,
     if (pkt)
         ctx->done_first_au = 1;
 
-    return err;
+    return 0;
 }
 
 static const CBSBSFType h264_metadata_type = {