When using the "stat.child.0" syntax to add Statistics instances to steady-state evolution, the method SteadyStateEvolutionState.checkStatistics(), which is called from setup(), assumes that the "base" Parameter passed in will have the value P_STATISTICS.
In fact, the base Parameter used by SteadyStateEvolutionState.setup() is null, so we get a NPE during initialization.
A simple fix is to replace "base" with "new Parameter(P_STATISTICS)" in the call to checkStatistics on line 101.
Ph.D student in Computer Science
George Mason University