课程配置删除唯一的课程体系不成功

app/controllers/admins/subject_settings_controller.rb

@@ -8,16 +8,15 @@ class Admins::SubjectSettingsController < Admins::BaseController
   end
 
   def update
-    if params[:sub_disciplines]
-      sub_ids = params[:sub_disciplines].reject(&:blank?).map(&:to_i)
-      old_sub_ids = current_subject.sub_discipline_containers.pluck(:sub_discipline_id)
-      new_ids = sub_ids - old_sub_ids
-      delete_ids = old_sub_ids - sub_ids
-      sub_params = new_ids.map{|sub| {sub_discipline_id: sub}}
-      ActiveRecord::Base.transaction do
-        current_subject.sub_discipline_containers.where(sub_discipline_id: delete_ids).destroy_all
-        current_subject.sub_discipline_containers.create!(sub_params)
-      end
+    sub_discipline_ids = params[:sub_disciplines] || []
+    sub_ids = sub_discipline_ids.reject(&:blank?).map(&:to_i)
+    old_sub_ids = current_subject.sub_discipline_containers.pluck(:sub_discipline_id)
+    new_ids = sub_ids - old_sub_ids
+    delete_ids = old_sub_ids - sub_ids
+    sub_params = new_ids.map{|sub| {sub_discipline_id: sub}}
+    ActiveRecord::Base.transaction do
+      current_subject.sub_discipline_containers.where(sub_discipline_id: delete_ids).destroy_all
+      current_subject.sub_discipline_containers.create!(sub_params)
     end
   end