"There is already an account of this type with that username created." when adding FreshRSS login

[ITistheworst]

When adding a FreshRSS account on NNW for MacOS I got the error 'There is already an account of this type with that username created.'. As FreshRSS is instance dependent the same username can be present on multiple instances and still be differet accounts. This check may need to be tweaked to only trigger if the API url is the same (or maybe include a continue anyway option).