SOCKETFUNCTION receives zero fd and socket_data for HTTP/3 connections

[sfionov]

That leads to stalled reads.

I did this

1. Set CURLMOPT_SOCKETFUNCTION to start polling on socket
2. Start request

socketfunction sometimes receives zero fd to poll, and also zero socket_data for it, with "IN" action.

As result, HTTP/3 connection becoming very slow because it can do reads only when some timeout is fired.

I expected the following

socketfunction NEVER receives zero fd to poll (why to poll stdin?), and also zero socket_data for it.

curl/libcurl version

libcurl 7.88.1 with ngtcp2 0.13.1 and nghttp2 0.7.1

It worked ok on libcurl 7.85 + ngtcp2 0.9.0

operating system

macOS 12.6

[icing]

Please see #10595 for the fix and description of this issue.