Fix Active Record errors deprecation warning

app/models/concerns/pageflow/reusable_file.rb

@@ -30,16 +30,16 @@ def parent_allows_type_for_nesting
         file_type_of_parent = Pageflow.config.file_types.find_by_model!(parent_class)
         models_of_nested_file_types = file_type_of_parent.nested_file_types.map(&:model)
         unless models_of_nested_file_types.include?(self.class)
-          errors[:base] << 'File type of provided parent file does not permit nesting files of '\
-                           "type #{self.class.name}"
+          errors.add(:base, 'File type of provided parent file does not permit nesting files of '\
+                            "type #{self.class.name}")
         end
       end
     end
 
     def parent_belongs_to_same_entry
       if parent_file.present?
         unless parent_file.using_entries.include?(entry)
-          errors[:base] << 'Parent file does not belong to same entry as nested file'
+          errors.add(:base, 'Parent file does not belong to same entry as nested file')
         end
       end
     end

app/models/pageflow/membership.rb

@@ -38,8 +38,9 @@ class Membership < ApplicationRecord
     private
 
     def account_membership_exists
-      errors[:base] << 'Entry Membership misses presupposed Membership on account of entry' if
-        user.present? && !user.accounts.include?(entity.account)
+      return if user.blank? || user.accounts.include?(entity.account)
+
+      errors.add(:base, 'Entry Membership misses presupposed Membership on account of entry')
     end
 
     def on_entry?