Merge branch '6.4' into 7.0

* 6.4:
  fix typo
  Add types to private and internal properties
  [Workflow] Cleaning code
  [Scheduler] Fix NPE in debug:scheduler command

Author: nicolas-grekas

ErrorHandler.php

@@ -96,6 +96,7 @@ class ErrorHandler
 
     private bool $isRecursive = false;
     private bool $isRoot = false;
+    /** @var callable|null */
     private $exceptionHandler;
     private ?BufferingLogger $bootstrappingLogger = null;