Links to add code branches is hidden if a project has no branches

[Andrea Corbellini]

Steps to reproduce:

1. register a new project;
2. set the maintainer of the project to an another person or a team you do not own;
3. go to the code tab and look for a way to register new branches or new imports.

From the UI, there are not ways to access +addbranch or +new-import, although those pages are actually accessible.
This is an annoying problem if you want to setup a code import for a project that is already registered but maintained by ~registry or some other people.