Fatal error – edit menu

Hi everybody,

I have inserted the event calendar page as the homepage of the site and when I want to edit the menu, it gives me a fatal error:

Fatal error: uncaught Error: Attempt to assign property “front_or_home” on null in /data/web/virtuals/308478/virtual/www/domains/nazevwebu/wp-admin/includes/nav-menu.php:379 Stack trace: #0 /data/web/virtuals/308478/virtual/www/domains/nazevwebu/wp-admin/includes/template. php(1528): wp_nav_menu_item_post_type_meta_box(NULL, Array) #1 /data/web/virtuals/308478/virtual/www/domains/nazevwebu/wp-admin/nav-menus. php(945): do_accordion_sections(Object(WP_Screen), ‘side’, NULL) #2 {main} thrown in /data/web/virtuals/308478/virtual/www/domains/nazevwebu/wp-admin/includes/nav-menu.php on line 379

Any idea what I should edit in nav-menu.php, nav-menus.php and template.php to make it ok?

Thank you for help.