Prevent deleting the static page doc topics

lib/guardian/topic_guardian.rb

@@ -41,7 +41,8 @@ module TopicGuardian
   def can_delete_topic?(topic)
     !topic.trashed? &&
     is_staff? &&
-    !(Category.exists?(topic_id: topic.id))
+    !(Category.exists?(topic_id: topic.id)) &&
+    !Discourse.static_doc_topic_ids.include?(topic.id)
   end
 
   def can_reply_as_new_topic?(topic)

spec/components/guardian_spec.rb

@@ -1024,6 +1024,12 @@ describe Guardian do
       it 'returns true when an admin' do
         Guardian.new(admin).can_delete?(topic).should be_true
       end
+
+      it 'returns false for static doc topics' do
+        tos_topic = Fabricate(:topic, user: Discourse.system_user)
+        SiteSetting.stubs(:tos_topic_id).returns(tos_topic.id)
+        Guardian.new(admin).can_delete?(tos_topic).should be_false
+      end
     end
 
     context 'a Post' do
@@ -1064,6 +1070,14 @@ describe Guardian do
         Guardian.new(admin).can_delete?(post).should be_true
       end
 
+      it 'returns false when post is first in a static doc topic' do
+        tos_topic = Fabricate(:topic, user: Discourse.system_user)
+        SiteSetting.stubs(:tos_topic_id).returns(tos_topic.id)
+        post.update_attribute :post_number, 1
+        post.update_attribute :topic_id, tos_topic.id
+        Guardian.new(admin).can_delete?(post).should be_false
+      end
+
       context 'post is older than post_edit_time_limit' do
         let(:old_post) { build(:post, topic: topic, user: topic.user, post_number: 2, created_at: 6.minutes.ago) }
         before do