MDL-77350 comment: Added class properties that are not declared

In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.

comment/lib.php

@@ -96,6 +96,8 @@ class comment {
     private static $comment_page = null;
     /** @var string comment itemid component in non-javascript UI */
     private static $comment_component = null;
+    /** @var stdClass comment paramaters for callback. */
+    protected $comment_param;
 
     /**
      * Construct function of comment class, initialise