[InterNetNews/inn] 28d93e: Print a warning in CHANcreate, not returning NULL

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 28d93e34b92d322e00f22f539623fc5716dce289
      https://github.com/InterNetNews/inn/commit/28d93e34b92d322e00f22f539623fc5716dce289
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2023-07-09 (Sun, 09 Jul 2023)

  Changed paths:
    M innd/chan.c

  Log Message:
  -----------
  Print a warning in CHANcreate, not returning NULL

Let's play safe, and not return NULL when the file descriptor is too
large.  The rest of the code currently does not handle such a response,
but ensures the file descriptor is valid before calling CHANcreate().

see #273