Developers cannot create new projects

In https://gitlab.com/gitlab-org/gitlab-ee/issues/2534, we added the ability to allow developers to create projects within a group. However, there seems to be a regression which doesn't allow developers to create projects even when the group setting allows for it.

To reproduce:

1. Within a group, change the setting for Allowed to create projects to Developers + Masters
2. Add a member to the group with the developer role
3. As a developer, click "Create project" button on the group details view
4. Project path is set to namespace greyed out on project creation page