Propagators conversion
The method convert(Propagator propagator, ...), from the AbstractPropagatorConverter class, throws an OrekitException if the propagator to be converted doesn't accept to reset its initial state, like the TLEPropagator (and some others). But in this case, it doesn't really matter if the propagator can't be reset.
Surrounding the instruction "source.resetInitialState(initialState)" with a try/catch doing nothing when catching a PropagationException will permit to convert directly such propagators.
(from redmine: issue id 335, created on 2017-04-13, closed on 2017-07-27)