Fix unavailable project download after cloning

1. clone a project (in my case source as master branch and target as master branch)
2. reload the page
3. double-check the project has been cloned correctly and datas are present
4. try to download the project -> redirection to an error page

Workaround (thanks to Nico):

1. modify the project (for example create an empty schema) and save
2. try to download the project again -> it works