Fix bug.

app/controllers/admin/asks_controller.rb

@@ -196,7 +196,7 @@ class Admin::AsksController < OrbitAdminController
                                  .any_in(:identity => filter2("identity"))
                                  .any_in(:situation => filter2("situation"))
     end
-    @askquestions = @askquestions.where(:category_id=>category_id)
+    @askquestions = @askquestions.where(:category_id=>category_id) if category_id
     # 分頁
     @askquestions = search_data(@askquestions,[:title]).page(params[:page]).per(10)
     if request.xhr?