400 Error

Hi,

when I try and activate other icon types trough the settings, the spinner never stops after I click on Save and I see the following in Console (400 error on the second line on POST from /wp-admin/admin-ajax.php?action=menu_icons_update_settings):

load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:9 JQMIGRATE: Migrate is installed, version 1.4.1
load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:4 POST /wp-admin/admin-ajax.php?action=menu_icons_update_settings 400 ()
send @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:4
ajax @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:4
(anonymous) @ admin.min.js?ver=0.11.0:1
dispatch @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:3
r.handle @ load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,utils,jquery-ui-widget,jquery-ui-core,jquery-ui-mouse,jquery-ui-sortable,jquery-ui-draggable,jquery-u&load[]=i-droppable,wp-ajax-response,jquery-color,wp-lists,postbox,nav-menu,moxiejs,plupload&ver=4.9.4:3

Any idea why that is?