[PostSets] Fix exception on admin update

This code path had a few issues which weren't triggered previously.
Also changes the visibility change modaction to track the new visibility.

app/controllers/post_sets_controller.rb

@@ -53,11 +53,11 @@ class PostSetsController < ApplicationController
 
     unless @post_set.is_owner?(CurrentUser.user)
       if @post_set.saved_change_to_is_public?
-        ModAction.log(:set_mark_private, {set_id: @post_set.id, user_id: @post_set.creator_id})
+        ModAction.log(:set_change_visibility, { set_id: @post_set.id, user_id: @post_set.creator_id, is_public: @post_set.is_public })
       end
 
-      if @post_set.saved_change_to_watched_attribute?
-        Modaction.log(:set_update, {set_id: @post_set.id, user_id: @post_set.creator_id})
+      if @post_set.saved_change_to_watched_attributes?
+        ModAction.log(:set_update, { set_id: @post_set.id, user_id: @post_set.creator_id })
       end
     end
 

app/decorators/mod_action_decorator.rb

@@ -100,8 +100,8 @@ class ModActionDecorator < ApplicationDecorator
 
       ### Set ###
 
-    when "set_mark_private"
-      "Made set ##{vals['set_id']} by #{user} private"
+    when "set_change_visibility"
+      "Made set ##{vals['set_id']} by #{user} #{vals['is_public'] ? 'public' : 'private'}"
     when "set_update"
       "Edited set ##{vals['set_id']} by #{user}"
     when "set_delete"

app/models/mod_action.rb

@@ -46,7 +46,7 @@ class ModAction < ApplicationRecord
       :report_reason_update,
       :set_update,
       :set_delete,
-      :set_mark_private,
+      :set_change_visibility,
       :tag_alias_create,
       :tag_alias_update,
       :tag_implication_create,

app/models/post_set.rb

@@ -66,7 +66,7 @@ class PostSet < ApplicationRecord
   end
 
   def saved_change_to_watched_attributes?
-    saved_change_to_name? || saved_change_to_shortname? || saved_change_to_description?
+    saved_change_to_name? || saved_change_to_shortname? || saved_change_to_description? || saved_change_to_transfer_on_delete?
   end
 
   module ValidationMethods