converse.js prebind authentication gives a fatal error

Question

I am using prebind authentication in converse.js. When I initialize converse, I receive the error:

"FATAL: TypeError: Cannot read property 'insertAdjacentElement' of null"

The error can be traced back to converse-register.js:57, where this.el.querySelector('.buttons') is set to null because, presumably, the querySelector function cannot find any elements. This error occurs when using prebind authentication but not login authentication. Any thoughts on what might be causing this?

If it makes a difference, this is my converse.initialize script:

converse.initialize({
    locales_url: 'apps/view/javascript/converse/locale/ro/LC_MESSAGES/converse.json',
    bosh_service_url: 'http://localhost:5443/bosh',
    debug: true,
    prebind_url: 'http://localhost/index.php? route=common/login/prebind',
    authentication: 'prebind',
    allow_logout: false,
    keepalive: true,
    message_carbons: true,
    play_sounds: true,
    roster_groups: true,
    show_controlbox_by_default: true,
    xhr_user_search: false
});