Commit links in blame view broken when using custom domain (BB-12026)

When browsing bitbucket using whatever.mydomain.com and browsing the blame view for a given file, the links to individual commits point to

http://whatever.mydomain.com/myaccount/myrepository/commits/[commitnumber]

rather than

http://whatever.mydomain.com/myrepository/commits/[commitnumber]

(in other words myaccount gets added to the url, despite it being a custom domain)