Correct some bugs

This is a correction of some bugs.

These two lines bellow need to define a strategy in case of an error/yield is receive witout an invocation.
if(handler.pendingInvocations == null) return;  // If a client send a yield without an invocation, return
if(from.pendingInvocations == null) return; // if an error is send before an invocation, do not do anythin

Strategy here is to ignore when something goes wrong.