avcodec/av1_parser: don't abort parsing the first frame if extradata parsing fails

The first frame contains the sequence header, which is needed to parse every
following frame.

This fixes parsing streams with broken extradata but correct packet data.
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/av1_parser.c

@@ -68,8 +68,7 @@ static int av1_parser_parse(AVCodecParserContext *ctx,
 
         ret = ff_cbs_read(s->cbc, td, avctx->extradata, avctx->extradata_size);
         if (ret < 0) {
-            av_log(avctx, AV_LOG_ERROR, "Failed to parse extradata.\n");
-            goto end;
+            av_log(avctx, AV_LOG_WARNING, "Failed to parse extradata.\n");
         }
 
         ff_cbs_fragment_reset(s->cbc, td);