am using Unite revolution slider 2 component, and in admin panel it doesnt show anything just this

error: [] operator not supported for strings

Joomla! 3.7.2

Php version: 7.1.0

slider version: cant recognize, maybe latest

forgot to mention, I enable error reporting to development, and enable debug mode

and got this call stack

#     Function                             Location
1     UniteBaseAdminClassRev::addMetaBox() :   
JROOT/administrator/components/com_uniterevolution2/revslider_admin.php:79

2     RevSliderAdmin->addSliderMetaBox() :    
JROOT/administrator/components/com_uniterevolution2/revslider_admin.php:61

3     RevSliderAdmin->init()                    
JROOT/administrator/components/com_uniterevolution2/revslider_admin.php:31

4     RevSliderAdmin->__construct()            
JROOT/administrator/components/com_uniterevolution2/uniterevolution2.php:39

5     require_once()                     
JROOT/libraries/cms/component/helper.php:394

6     JComponentHelper::executeComponent()    
JROOT/libraries/cms/component/helper.php:369

7     JComponentHelper::renderComponent()   
 JROOT/libraries/cms/application/administrator.php:98

8     JApplicationAdministrator->dispatch()  
  JROOT/libraries/cms/application/administrator.php:156

9     JApplicationAdministrator->doExecute()   
 JROOT/libraries/cms/application/cms.php:265

10     JApplicationCms->execute()          
  JROOT/administrator/index.php:51

Thanks let me try