ActionView::Template::Error (undefined method `human_name' for nil:NilClass)

Just updated to Gitlab 7.13 and now, when I edit a project I get:

ActionView::Template::Error (undefined method `human_name' for nil:NilClass):
178: %span Namespace
179: .col-sm-9
180: .form-group
181: = select_tag :new_namespace_id, namespaces_options(@project.namespace_id), { prompt: 'Choose a project namespace', class: 'select2' }
182: %ul
183: %li Be careful. Changing the project's namespace can have unintended side effects.
184: %li You can only transfer the project to namespaces you manage.
app/helpers/namespaces_helper.rb:7:in `each'
app/helpers/namespaces_helper.rb:7:in `sort_by'
app/helpers/namespaces_helper.rb:7:in `namespaces_options'
app/views/projects/edit.html.haml:181:in `block in _app_views_projects_edit_html_haml___1871016317433513050_70247062878880'
app/views/projects/edit.html.haml:175:in `_app_views_projects_edit_html_haml___1871016317433513050_70247062878880'
app/controllers/projects_controller.rb:18:in `edit'