Make `failure` parameter of `Popover.ajaxApi()` optional
Make `failure` parameter of `Popover.ajaxApi()` optional

There is no reason to make the custom failure callback a required parameter here because in most cases, there is no need fur such a custom handler.

SoftCreatR/WCF,Cyperghost/WCF,WoltLab/WCF,WoltLab/WCF,WoltLab/WCF,SoftCreatR/WCF,Cyperghost/WCF,WoltLab/WCF,Cyperghost/WCF,SoftCreatR/WCF,Cyperghost/WCF,SoftCreatR/WCF,Cyperghost/WCF