Issue #3232001: activity tracker cron calls \Drupal::service('comment.statistics')->read in a wrong way

This commit fixes an issue in _tracker_calculate_changed function in tracker.module.

The commit resolves two issues:

• Fixed an issue where an entity key was not associated with the node object
• The code did not properly check if the datatype was an array and improperly accessed the array as if it was an object

closed