Can't activate / deactivate extra tabs on product sheet

hello I changed my template two days ago and i have a problem with "extra tabs" module now in cataloge->products->edit->extratabpro i cant enable and disable tab.



Hello,
Issue is not related to "extra tabs pro".  There is an error in override:

<br />
<b>Fatal error</b>:  Class 'Mobile_Detect' not found in <b>/home/dayabarg/public_html/override/classes/controller/FrontController.php</b> on line <b>22</b><br />

simply saying override file has an error because "mobile_detect" class does not exist. 
Code that is responsible for this error is located in file: /override/classes/controller/FrontController.php

//require_once(_PS_TOOL_DIR_.'mobile_Detect/Mobile_Detect.php');
 $this->mobile_detect = new Mobile_Detect();
 $mobile_class = 'desktop';
 if ($this->mobile_detect->isMobile()){
  $mobile_class = 'mobile';
 }        

You will have the same problem for all other modules that uses "ajax" requests for example "homepage slider" or "wtslideshow". Try to change position of the slide, you will have the same error (changes will not be saved).

how to fix?
it is required to uncomment

//require_once(_PS_TOOL_DIR_.'mobile_Detect/Mobile_Detect.php');