multi: Fix curl_multi_poll wait when extra_fds && !extra_nfds

Prior to this change:

The check if an extra wait is necessary was based not on the
number of extra fds but on the pointer.

If a non-null pointer was given in extra_fds, but extra_nfds
was zero, then the wait was skipped even though poll was not
called.

Closes https://github.com/curl/curl/pull/4610

0 files changed, 0 insertions, 0 deletions