Fix PHP 8.1 "strlen(null)" exception which blocks rendering list of Active/All projects

`strlen()` was used in Phabricator to check if a generic value is a non-empty string.
This behavior is deprecated since PHP 8.1. Phorge adopts `phutil_nonempty_string()` as a replacement.

Note: this may highlight other absurd input values that might be worth correcting
instead of just ignoring. If phutil_nonempty_string() throws an exception in your
instance, report it to Phorge to evaluate and fix that…
Repository: rP Phorge
Author: aklapper
Commit Date: May 1 2023