Editing group label resulting in error 404

Summary

Editing a group label results in a 404 error

Steps to reproduce

• create a group label
• try to edit the newly created group label, notice the 404 error

Expected behavior

Be offered to edit the label data (name, description, color)

Relevant logs and/or screenshots

Started GET "/groups/group/labels/label-id/edit" for ip at 2016-11-30 12:01:14 +0100
Processing by GroupsController#edit as HTML
Parameters: {"id"=>"group/labels/label-id"}
Filter chain halted as :group rendered or redirected
Completed 404 Not Found in 35ms (Views: 0.5ms | ActiveRecord: 2.1ms)
Started GET "/groups/group/labels/label-id/edit" for ip at 2016-11-30 12:01:14 +0100
Processing by GroupsController#edit as HTML
Parameters: {"id"=>"group/labels/label-id"}
Filter chain halted as :group rendered or redirected
Completed 404 Not Found in 35ms (Views: 0.4ms | ActiveRecord: 2.1ms)

Results of GitLab environment info

System information
System:		Debian 8.6
Current User:	git
Using RVM:	no
Ruby Version:	2.3.1p112
Gem Version:	2.6.8
Bundler Version:1.13.6
Rake Version:	10.5.0
Sidekiq Version:4.2.1

GitLab information
Version:	8.15.0-pre
Revision:	7cb2028
Directory:	/home/git/gitlab
DB Adapter:	mysql2
URL:		https://git.domain.tld
HTTP Clone URL:	https://git.domain.tld/some-group/some-project.git
SSH Clone URL:	git@git.domain.tld:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: github, bitbucket, gitlab, google_oauth2, twitter

GitLab Shell
Version:	4.0.2
Repository storage paths:
- default: 	/home/git/repositories/
Hooks:		/home/git/gitlab-shell/hooks/
Git:		/usr/bin/git