Root breadcrump is losing context (BB-3579)

Clicking the root breadcrump while browsing a tree at the time of a specific cs will loose that context and default to the tip of master again.

E.g. https://bitbucket.org/atlassian/aui-archive/src/77557c1443ba/auiplugin/src, clicking the aui-archive breadcrump (root) in the path will loose the cs hash 77557c1443ba, it just points to https://bitbucket.org/atlassian/aui-archive/src but the aui-plugin breadcrump before is linked correctly to https://bitbucket.org/atlassian/aui-archive/src/77557c1443ba/auiplugin/. So aui-archive should link to https://bitbucket.org/atlassian/aui-archive/src/77557c1443ba instead of https://bitbucket.org/atlassian/aui-archive/src