取不到学校，再拿id直接空指针

app/controllers/welcome_controller.rb

@@ -33,7 +33,7 @@ class WelcomeController < ApplicationController
     if params[:school_id]
       @school_id = params[:school_id]
     elsif User.current.logged?  && User.current.user_extensions.school
-      @school_id = User.current.user_extensions.school.id
+      @school_id = User.current.user_extensions.school.try(:id)
     end
     @logoLink ||= logolink()
   end