rtpenc_mpegts: Free the right ->pb in the error path in the init function

This fixes a typo from 8e32b1f096.

Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtpenc_mpegts.c

@@ -98,7 +98,7 @@ static int rtp_mpegts_write_header(AVFormatContext *s)
 
 fail:
     if (mpegts_ctx) {
-        ffio_free_dyn_buf(&chain->mpegts_ctx->pb);
+        ffio_free_dyn_buf(&mpegts_ctx->pb);
         avformat_free_context(mpegts_ctx);
     }
     if (rtp_ctx)