When reordering book pages at admin/content/book/%node, you get the following fatal error:
Fatal error: Call to a member function save() on a non-object in core/modules/menu_link/menu_link.module on line 120It looks like a regression after the menu_link conversion. book_menu_subtree_data() returns an array of menu links, which book_admin_edit_submit() then calls a direct menu_link_save() on.
Tests are also needed, since testbot isn't catching this.