Fix broken group avatar upload

Closes #3918

CHANGELOG

@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.3.0 (unreleased)
   - Bump gollum-lib to 4.1.0 (Stan Hu)
+  - Fix broken group avatar upload under "New group" (Stan Hu)
   - Fix API setting of 'public' attribute to false will make a project private (Stan Hu)
   - Handle and report SSL errors in Web hook test (Stan Hu)
   - Fix: Assignee selector is empty when 'Unassigned' is selected (Jose Corcuera)

app/assets/javascripts/dispatcher.js.coffee

@@ -83,7 +83,7 @@ class Dispatcher
       when 'projects:project_members:index'
         new ProjectMembers()
         new UsersSelect()
-      when 'groups:new', 'groups:edit', 'admin:groups:edit'
+      when 'groups:new', 'groups:edit', 'admin:groups:edit', 'admin:groups:new'
         new GroupAvatar()
       when 'projects:tree:show'
         new TreeView()