Fix PHP 8.1 "strlen(null)" exceptions which block rendering the DarkConsole

Summary:
Since PHP 8.1 the function call `strlen(null)` is deprecated.

Since Phabricator/Phorge elevates deprecation warnings to exceptions, the
specific fix implies dealing with null, and dealing with real strings.

In the specific case, a simple cast was made to deal with real strings.

Closes T15315

Test Plan: Visit the Home Page with DarkConsole enabled in your configuration: no crashes

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: aklapper, speck, tobiaswiese, Matthew, Cigaryno

Maniphest Tasks: T15315

Differential Revision: https://we.phorge.it/D25165

src/applications/console/core/DarkConsoleCore.php

@@ -124,6 +124,9 @@ final class DarkConsoleCore extends Phobject {
     } else if (is_resource($data)) {
       return '<resource>';
     } else {
+      // This is very probably not a string in strict sense
+      $data = phutil_string_cast($data);
+
       // Truncate huge strings. Since the data doesn't really matter much,
       // just truncate bytes to avoid PhutilUTF8StringTruncator overhead.
       $length = strlen($data);