Fix PHP 8.1 "strlen(null)" exception which blocks rendering Config's Database Status page

Summary:
`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 T15428

Test Plan:
Applied this change; afterwards displays "Database Status" page at `/config/database/` correctly rendered in web browser.

Also visit every single database name, to see that also there nothing explode.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15428

Differential Revision: https://we.phorge.it/D25260

src/applications/config/controller/services/PhabricatorConfigDatabaseStatusController.php

@@ -837,7 +837,7 @@ final class PhabricatorConfigDatabaseStatusController
 
     $parts = array();
     foreach ($properties as $key => $property) {
-      if (!strlen($property)) {
+      if (!phutil_nonempty_string($property)) {
         continue;
       }