avcodec/bsf: Don't set defaults for AVClass without options

This happened for AVBSFContext.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/bsf.c

@@ -45,8 +45,6 @@ void av_bsf_free(AVBSFContext **pctx)
     if (ctx->filter->priv_class && ctx->priv_data)
         av_opt_free(ctx->priv_data);
 
-    av_opt_free(ctx);
-
     if (ctx->internal)
         av_packet_free(&ctx->internal->buffer_pkt);
     av_freep(&ctx->internal);
@@ -112,8 +110,6 @@ int av_bsf_alloc(const AVBitStreamFilter *filter, AVBSFContext **pctx)
         goto fail;
     }
 
-    av_opt_set_defaults(ctx);
-
     /* allocate priv data and init private options */
     if (filter->priv_data_size) {
         ctx->priv_data = av_mallocz(filter->priv_data_size);