Fix load_refs in ApplicationController after default_branch change

As a last resort it was calling a method that didn't exist. Woops!

app/controllers/application_controller.rb

@@ -124,7 +124,7 @@ class ApplicationController < ActionController::Base
     if params[:ref].blank?
       @branch = params[:branch].blank? ? nil : params[:branch]
       @tag = params[:tag].blank? ? nil : params[:tag]
-      @ref = @branch || @tag || @project.try(:default_branch) || Repository.default_ref
+      @ref = @branch || @tag || @project.try(:default_branch) || 'master'
     else
       @ref = params[:ref]
     end