When I create a pull request based on an orphan branch (special branch type in Git), then Tuleap raises errors and seems unable to even display the user interface.

Instead, it should display the user interface and let people at least close the pull request. Ideally Tuleap should be able to merge the branch, but that is nice-to-have and could be the subject of another request.

Here is the reproduction scenario:

• Create a git repository on Tuleap

# Clone the Tuleap repository locally
# …
$ git checkout --orphan=orphan_branch
# Create a file README.txt and write some text in it
$ git add README.txt
$ git commit
$ git push origin orphan_branch

• Then create a pull request from orphan_branch to the default branch of the repository.