Fix usage of nil primary key in tree builders related to active records

Author: atranson-electra

lib/super_diff/active_record/inspection_tree_builders/active_record_model.rb

@@ -27,7 +27,11 @@ def call
 
             t1.nested do |t2|
               t2.insert_separated_list(
-                [id] + (object.attributes.keys.sort - [id])
+                if id.nil?
+                  object.attributes.keys.sort
+                else
+                  [id] + (object.attributes.keys.sort - [id])
+                end
               ) do |t3, name|
                 t3.as_prefix_when_rendering_to_lines do |t4|
                   t4.add_text "#{name}: "

lib/super_diff/active_record/operation_tree_builders/active_record_model.rb

@@ -16,6 +16,8 @@ def id
         end
 
         def attribute_names
+          return expected.attributes.keys.sort if id.nil?
+
           [id] + (expected.attributes.keys.sort - [id])
         end
       end