导入的试卷进入查看页报500

app/controllers/exercise_controller.rb

@@ -56,7 +56,7 @@ class ExerciseController < ApplicationController
       end
     end
     @is_teacher = User.current.allowed_to?(:as_teacher,@course) || User.current.admin?
-    exercise_end = @exercise.end_time > Time.now
+    exercise_end = @exercise.end_time.nil? ? false : @exercise.end_time > Time.now
     if @exercise.time == -1
       @can_edit_excercise = exercise_end
     else

app/views/exercise/_exercise_teacher.html.erb

@@ -13,7 +13,9 @@
         <% unless exercise.publish_time.nil? %>
             <span class="mr100">发布时间：<%=Time.parse(h(exercise.publish_time)).strftime("%Y-%m-%d %H:%M:%S") %></span>
         <% end %>
-        <span class="mr100">截止时间：<%=Time.parse(h(exercise.end_time)).strftime("%Y-%m-%d %H:%M:%S") %></span>
+        <% unless exercise.end_time.nil? %>
+            <span class="mr100">截止时间：<%=Time.parse(h(exercise.end_time)).strftime("%Y-%m-%d %H:%M:%S") %></span>
+        <% end %>
         <% if exercise.time != -1 %>
             <span class="fr">测验时长：<%=exercise.time %>分钟</span>
         <% end %>