课程动态，无对应数据时报错

app/helpers/courses_helper.rb

@@ -682,6 +682,7 @@ module CoursesHelper
     # activity = CourseActivity.first
     title = ""
     url = ""
+    if activity.course_act
       case activity.course_act_type
         when "Course"
           title = activity.course_act.name
@@ -705,6 +706,7 @@ module CoursesHelper
           title = "问卷 " + activity.course_act.polls_name
           url = poll_index_path(:polls_type => "Course", :polls_group_id => activity.course_id)
       end
+    end
     link_to title.gsub(/<(?!img)[^>]*>/,'').html_safe, url, :class => "problem_tit c_dblue fl fb"
   end