PHP 8 and Diviner Technical Documentation

Summary:
This also fixes the field Personal Settings > Display Preferences > Monospaced Font, when empty.

Close T15621

Test Plan: Generate diviner stuff, navigate to the "Technical Documentation" section (In php 8.1+)

Reviewers: O1 Blessed Committers, mturdus, valerio.bozzolan

Reviewed By: O1 Blessed Committers, mturdus, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15621

Differential Revision: https://we.phorge.it/D25412

Author: avivey

src/applications/diviner/storage/DivinerLiveSymbol.php

@@ -172,7 +172,7 @@ public function save() {
   public function getTitle() {
     $title = parent::getTitle();
 
-    if (!strlen($title)) {
+    if (!phutil_nonempty_string($title)) {
       $title = $this->getName();
     }
 

src/applications/settings/setting/PhabricatorMonospacedFontSetting.php

@@ -25,7 +25,7 @@ protected function getControlInstructions() {
   }
 
   public function validateTransactionValue($value) {
-    if (!strlen($value)) {
+    if (!phutil_nonempty_string($value)) {
       return;
     }