Shop::createExplicitInteraction is not fully compatible with RungeKuttaCashKarp54Integrator

Shop::createExplicitInteraction is looping through the engines to find IGeom, IPhys. But RungeKuttaCashKarp54Integrator keeps them inside itself. Present workaround is to add a dead InteractionLoop in the O.engines loop with IGeom + IPhys in it. Better solution is welcome.