Retropropagation issue in AbstractPropagator.acceptedStep
If eventStates are not yet initialized, a propagation is performed at
the previous date (ie initialState), resulting in a retropropagation,
even if there is no actual event Handler !
It becomes troublesome if the propagator cannot do retropropagation.
Suggested workaround: adding a <if (!eventStates.isEmpty())> condition
inside the <if (!statesInitialized)>
Suggested and prefered correction: saving the event handler states when
performing a setInitialStep.
(from redmine: issue id 107, created on 2012-07-31, closed on 2012-07-31)