Why does Trigger.new.size() throw a NullPointerException in a delete trigger while Trigger.size works?

Trigger.size returns the number of records in the current invocation and works in every event. Trigger.new.size() fails with a NullPointerException in delete triggers because Trigger.new is null there (only Trigger.old exists).

So shared logic that must handle delete should use Trigger.size or Trigger.isDelete ? Trigger.old.size() : Trigger.new.size(). In insert, update and undelete both return the same count (maximum 200 per chunk).