Fix "Register with Approval flow" for php 8

Summary: Ref T15064.

Test Plan:
- Register as a new user
- as admin, view user's page and approve it
- As new user, hit "wait patiently" to go back to Home

No crashes in this flow.

Reviewers: O1 Blessed Committers, chris

Reviewed By: O1 Blessed Committers, chris

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

Maniphest Tasks: T15064

Differential Revision: https://we.phorge.it/D25317

src/applications/auth/controller/PhabricatorAuthNeedsApprovalController.php

···
       $viewer,
       PhabricatorAuthWaitForApprovalMessageType::MESSAGEKEY);
 
-    if (!strlen($text)) {
+    if (!phutil_nonempty_string($text)) {
       return null;
     }
 

src/applications/auth/engine/PhabricatorAuthPasswordEngine.php

···
     $base_uri = new PhutilURI($base_uri);
     $blocklist[] = $base_uri->getDomain();
 
+    $blocklist = array_filter($blocklist);
+
     // Generate additional subterms by splitting the raw blocklist on
     // characters like "@", " " (space), and "." to break up email addresses,
     // readable names, and domain names into components.

src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php

···
   }
 
   public function renderPropertyViewValue(array $handles) {
-    if (!strlen($this->getFieldValue())) {
+    if (!phutil_nonempty_string($this->getFieldValue())) {
       return null;
     }
     return $this->getFieldValue();