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 specific corner case.

Closes T15305

Applied these two changes (on top of D25144, D25145, D25146, D25147, D25150,
D25151, D25152, D25153, D25154)) and "Use Results -> Add Panel to Dashboard"
overlay dialog finally rendered in web browser.