Defines a strategy, used by Field components such as org.apache.tapestry5.corelib.components.TextField ,
to handle the case where either the server-side value to be sent (as a string) to the client, or the client-side
string passed back up to the server, is null or blank.
Provides a replacement value for a null or blank string passed from the client to the server as part of a form
submission. This replacement value will be passed to Translator#parseClient(Field, String, String) as if
it were the value supplied by the user.