ModelValidationEngine don't work as expected if no modelvalidators are found and fireFactsValidate don't send OSGI event

I found two problems with the ModelValidationEngine:

1 - if you disable the org.idempiere.fa.model.ModelValidator at the model validator window, the OSGi events are ignored.

2 - the method fireFactsValidate was not sending the event, and then, i'm unable to create a eventhandler for the ACCT_FACTS_VALIDATE topic.