Plugin could not be activated because it triggered a fatal error, Error during revslider install

I have wordpress 4.9.5 and revolution slider 5.1.

i am using “https://themeforest.net/item/mono-creative-multipurpose-wordpress-theme/15706862” theme.

During revolution slider installation it gives me folllowing wrror.

Fatal error: Uncaught Error: [] operator not supported for strings in /home/myfolder/wp-content/plugins/revslider/includes/framework/base-admin.class.php:71 Stack trace: #0 /home/myfolder/wp-content/plugins/revslider/admin/revslider-admin.class.php(572): RevSliderBaseAdmin::addMetaBox(‘Revolution Slid…’, ‘’, Array, NULL) #1 /home/myfolder/wp-content/plugins/revslider/admin/revslider-admin.class.php(73): RevSliderAdmin->addSliderMetaBox() #2 /home/myfolder/wp-content/plugins/revslider/admin/revslider-admin.class.php(44): RevSliderAdmin->init() #3 /home/myfolder/wp-content/plugins/revslider/revslider.php(163): RevSliderAdmin->__construct(’/home/x9kv21q3d…’) #4 /home/myfolder/wp-admin/includes/plugin.php(1897): include(’/home/x9kv21q3d…’) #5 /home/x9kv21q3d2i6/public_html/clien in /home/myfolder/wp-content/plugins/revslider/includes/framework/base-admin.class.php on line 71

Author of theme
alenastudio

Contact the theme author instead posting the issue here