CI4.0rc3 + calling model->save() on unchanged entity causes critical error

it seems that calling a model's save() method on an unchanged instance of an Entity, causes
CRITICAL - 2019-11-24 17:57:19 --> You must use the "set" method to update an entry.
#0 /php/system/Database/BaseBuilder.php(2342): CodeIgniter\Database\BaseBuilder->validateUpdate()
#1 /php/system/Model.php(846): CodeIgniter\Database\BaseBuilder->update()
#2 /php/system/Model.php(533): CodeIgniter\Model->update(Array, Array)


The error message here does not help at all.

I was wondering if it is a bug? My suggestions would be:

• trying to save an unchanged entity should not cause error at all, or
  
• if it causes an error / exception, it should return a helpful message.