Fix PHP 8.1 auth view strlen(null) error

Summary:
Trying to view a Jira auth provider from https://my.phorge.site/auth/ results in strlen(): Passing null to parameter freebsd#1 ($string) of type string is deprecated

This change fixes it

Fixes T15634

Test Plan:
Go to https://my.phorge.site/auth/ and have a Jira already setup.
Click on Jira auth provider
Confirm the page is displayed and no error is generated.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15634

Differential Revision: https://we.phorge.it/D25432

Author: campbsb

Diff for: src/applications/auth/storage/PhabricatorAuthProviderConfigTransaction.php

@@ -150,7 +150,7 @@ public function getTitle() {
         $provider = $this->getProvider();
         if ($provider) {
           $title = $provider->renderConfigPropertyTransactionTitle($this);
-          if (strlen($title)) {
+          if (phutil_nonempty_string($title)) {
             return $title;
           }
         }