Merge branch 'fix/unexistent-group-500' into 'master'

Return a 404 instead of a 500 when accessing a non-existent group

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/3352

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/5600

See merge request !2614

CHANGELOG

@@ -8,6 +8,7 @@ v 8.5.0 (unreleased)
   - Fix diff comments loaded by AJAX to load comment with diff in discussion tab
   - Whitelist raw "abbr" elements when parsing Markdown (Benedict Etzel)
   - Don't vendor minified JS
+  - Display 404 error on group not found
   - Track project import failure
   - Fix visibility level text in admin area (Zeger-Jan van de Weg)
   - Update the ExternalIssue regex pattern (Blake Hitchcock)

app/controllers/groups_controller.rb

@@ -82,6 +82,7 @@ class GroupsController < Groups::ApplicationController
 
   def group
     @group ||= Group.find_by(path: params[:id])
+    @group || render_404
   end
 
   def load_projects

features/groups.feature

@@ -3,6 +3,10 @@ Feature: Groups
     Given I sign in as "John Doe"
     And "John Doe" is owner of group "Owned"
 
+  Scenario: I should not see a group if it does not exist
+    When I visit group "NonExistentGroup" page
+    Then page status code should be 404
+
   Scenario: I should have back to group button
     When I visit group "Owned" page
     Then I should see back to dashboard button

features/steps/groups.rb

@@ -120,6 +120,10 @@ class Spinach::Features::Groups < Spinach::FeatureSteps
     expect(page).to have_xpath("//span[@class='label label-warning']", text: 'archived')
   end
 
+  step 'I visit group "NonExistentGroup" page' do
+    visit group_path(-1)
+  end
+
   private
 
   def assigned_to_me(key)