Issue #3356962: Undefined property: DiffFormatter::$line_stats DiffEngine.php:861 with PHP 8

DiffEngine.php

@@ -799,6 +799,16 @@ class DiffFormatter {
    */
   var $trailing_context_lines = 0;
 
+  /**
+   * Keep track of lines.
+   *
+   * @var array
+   */
+  var $line_stats = array(
+    'counter' => array('x' => 0, 'y' => 0),
+    'offset' => array('x' => 0, 'y' => 0),
+  );
+
   /**
    * Format a diff.
    *