Fix Error 500 when global milestones have slashes

Closes #4226

CHANGELOG

@@ -3,6 +3,9 @@ Please view this file on the master branch, on stable branches it's out of date.
 v 8.4.0 (unreleased)
   - Implement new UI for group page
 
+v 8.3.1 (unreleased)
+  - Fix Error 500 when global milestones have slashes (Stan Hu)
+
 v 8.3.0
   - Add CAS support (tduehr)
   - Bump rack-attack to 4.3.1 for security fix (Stan Hu)

app/models/global_milestone.rb

@@ -16,7 +16,7 @@ class GlobalMilestone
   end
 
   def safe_title
-    @title.to_slug.to_s
+    @title.to_slug.normalize.to_s
   end
 
   def expired?

spec/models/global_milestone_spec.rb

@@ -62,4 +62,14 @@ describe GlobalMilestone, models: true do
       expect(@global_milestone.milestones.count).to eq(3)
     end
   end
+
+  describe :safe_title do
+    let(:milestone) { create(:milestone, title: "git / test", project: project1) }
+
+    it 'should strip out slashes and spaces' do
+      global_milestone = GlobalMilestone.new(milestone.title, [milestone])
+
+      expect(global_milestone.safe_title).to eq('git-test')
+    end
+  end
 end