Merge branch 'fix-issue-2555' into 'master'

Fix default avatars to ensure that helpers don't have /assets dir appended

See issue #2555

See merge request !1314

app/helpers/application_helper.rb

@@ -82,7 +82,7 @@ module ApplicationHelper
   end
 
   def default_avatar
-    image_path('no_avatar.png')
+    'no_avatar.png'
   end
 
   def last_commit(project)

app/helpers/auth_helper.rb

@@ -40,7 +40,7 @@ module AuthHelper
     if provider_has_icon?(provider)
       file_name = "#{provider.to_s.split('_').first}_#{size}.png"
 
-      image_tag(image_path("auth_buttons/#{file_name}"), alt: label, title: "Sign in with #{label}")
+      image_tag("auth_buttons/#{file_name}", alt: label, title: "Sign in with #{label}")
     else
       label
     end

app/helpers/groups_helper.rb

@@ -27,7 +27,7 @@ module GroupsHelper
     if group && group.avatar.present?
       group.avatar.url
     else
-      image_path('no_group_avatar.png')
+      'no_group_avatar.png'
     end
   end