Fatal Error

Plugin throws fatal error when saving rearranged assets. Here it is:

Fatal error: Uncaught TypeError: Cannot access offset of type string on string in \wp-content\plugins\gsp-assets-manager\gsp.php:114

Stack Trace
1.	
gsp_ajax_save('')
\wp-includes\class-wp-hook.php:307
2.	
WP_Hook->apply_filters('', Array)
\wp-includes\class-wp-hook.php:331
3.	
WP_Hook->do_action(Array)
\wp-includes\plugin.php:474
4.	
do_action('wp_ajax_gsp_sav...')
\wp-admin\admin-ajax.php:187
5.	
{main}
thrown in \wp-content\plugins\gsp-assets-manager\gsp.php on line 114