I wanted to mark the fawiki version of https://www.wikidata.org/wiki/Q40112 as a Good Article (it just got promoted as such). When I clicked on the badges icon next to its entry I got this error in the browser console: TypeError: this.options.badges.map is not a function. I reloaded the page in debug mode, and this is the part of jquery.wikibase.badgeselector.js that seems to trigger the error:
/**
* Fills the menu with a menu item for each badge that may be assigned.
*
* @return {jQuery.Promise}
* No resolved parameters.
* No rejected parameters.
*/
_fillMenu: function () {
var self = this,
deferred = $.Deferred(),
badgeIds = this.options.badges.map( function ( cssClasses, itemId ) {
return itemId;
} );