Critical error when updating GPP to 2.0.1

Hello,

I'm in the process of updating several sites and everything runs smoothly until I got a critical error with this one.
This site is in development since a couple of months already.
Please note that this error is NOT related to this snippet posted in my previous thread (not active here).

The error appears immediately after update and there is no error file logged.
I got the following on screen when enabling debug:

Fatal error: Uncaught Error: Call to undefined function gp_elements_sort_hierarchical_posts() 
in //...//wp-content/plugins/gp-elements-admin-link/gp-elements-admin.php:142 
Stack trace: 
#0 //...//wp-includes/class-wp-hook.php(292): gp_elements_admin_bar_links(Object(WP_Admin_Bar)) 
#1 //...//wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters(NULL, Array) 
#2 //...//wp-includes/plugin.php(551): WP_Hook->do_action(Array) 
#3 //...//wp-includes/admin-bar.php(95): do_action_ref_array('admin_bar_menu', Array) 
#4 //...//wp-includes/class-wp-hook.php(292): wp_admin_bar_render('') 
#5 //...//wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters('', Array) 
#6 //...//wp-includes/plugin.php(484): WP_Hook->do_action(Array) 
#7 /home/ppf in //...//wp-content/plugins/gp-elements-admin-link/gp-elements-admin.php on line 142

There has been a critical error on this website. 
Please check your site admin email inbox for instructions.

This displays only at backend - frontend displays the site normally.

Everything gets back to normal when GPP is reverted to previous version 1.12.3 but I now see that this line of the error still displays with "debug:true":

Notice: Trying to access array offset on value of type bool in //...//wp-content/plugins/gp-elements-admin-link/gp-elements-admin.php on line 54

I never noticed it before as I never enabled debug there but maybe it was already there since long time and doesn't seem to create other issues.