热门项目排序添加空值判断，默认按活跃度排序

app/controllers/welcome_controller.rb

@@ -32,7 +32,9 @@ class WelcomeController < ApplicationController
     @projects_all = Project.active.visible.
         joins("LEFT JOIN #{ProjectStatus.table_name} ON #{Project.table_name}.id = #{ProjectStatus.table_name}.project_id").
         where("#{Project.table_name}.project_type = ? and #{Project.table_name}.id in (?)", Project::ProjectType_project,@hot_projects_ids)
-
+    if @first_page.nil? ||  @first_page.sort_type.nil?
+      @projects = @projects_all.order("grade desc")
+    else
       case @first_page.sort_type
         when 0
           @projects =  @projects_all.order("created_on desc")
@@ -53,6 +55,8 @@ class WelcomeController < ApplicationController
       end
     end
 
+  end
+
   def robots
     @projects = Project.all_public.active
     render :layout => false, :content_type => 'text/plain'