试卷库的调整

app/views/examination_banks/show.json.jbuilder

@@ -45,7 +45,9 @@ json.exam do
     end
   end
   json.sub_discipline do
-    json.(@exam.sub_discipline, :id, :name)
+    if @exam.sub_discipline.present?
+      json.(@exam.sub_discipline, :id, :name)
+    end
   end
   json.tag_disciplines @exam.tag_disciplines do |tag|
     json.(tag, :id, :name)