Upload new avatars is not possible

[rich20]

Describe the bug
https://www.kunena.org/forum/36-German/158836-hochladen-von-neuem-avatar-funktioniert-nicht
Try it on k.org. Open the browser console and try to upload an avatar. you see this errors:

bootstrap.datepicker.js:837 Uncaught TypeError: Cannot read property '0' of undefined
at Datepicker.fillMonths (bootstrap.datepicker.js:837)
at new Datepicker (bootstrap.datepicker.js:151)
at HTMLDivElement. (bootstrap.datepicker.js:1649)
at Function.each (jquery.min.js?c7b36d4bd6be9e998aab13d1e5b3a074:2)
at a.fn.init.each (jquery.min.js?c7b36d4bd6be9e998aab13d1e5b3a074:2)
at a.fn.init.datepickerPlugin [as datepicker] (bootstrap.datepicker.js:1631)
at HTMLDocument. (profile.js:12)
at u (jquery.min.js?c7b36d4bd6be9e998aab13d1e5b3a074:2)
at Object.fireWith [as resolveWith] (jquery.min.js?c7b36d4bd6be9e998aab13d1e5b3a074:2)
at Function.ready (jquery.min.js?c7b36d4bd6be9e998aab13d1e5b3a074:2)