Merge pull request #15677 from sgrif/sg-less-imperative-pk

Use a conditional rather than early return in `id`

activerecord/lib/active_record/attribute_methods/primary_key.rb

@@ -15,9 +15,10 @@ def to_key
 
       # Returns the primary key value.
       def id
-        return unless self.class.primary_key
-        sync_with_transaction_state
-        read_attribute(self.class.primary_key)
+        if pk = self.class.primary_key
+          sync_with_transaction_state
+          read_attribute(pk)
+        end
       end
 
       # Sets the primary key value.