Cakephp 2.5.4 Error after adding DebugKit

As I followed the step by step given from this Youtube videos.

I'm very interested to know more about cakePhp. But unfortunately after I followed adding the DebugKit as Step 04 from the videos.

I got the following error message:

Notice (8): Trying to get property of non-object [APP\Plugin\DebugKit\Lib\Panel\HistoryPanel.php, line 48]
Notice (8): Trying to get property of non-object [APP\Plugin\DebugKit\Lib\Panel\SessionPanel.php, line 29]
Notice (8): Trying to get property of non-object [APP\Plugin\DebugKit\Lib\Panel\HistoryPanel.php, line 48]
Notice (8): Trying to get property of non-object [APP\Plugin\DebugKit\Lib\Panel\SessionPanel.php, line 29]
Fatal error: Call to a member function read() on a non-object in C:\xampp\htdocs\fgroup\cakephp\app\Plugin\DebugKit\Lib\Panel\SessionPanel.php on line 29

What should I do then to make it working perfectly?