Asserts are not checked when decision logic is empty in simulation

[lyg1597]

When no transitions are specified in the decision logic, the assertions are note checked. This happen because the guard and assertion checking are happened in the same function check_sim_transitions at simulator.py:728 and that line is executed only when there there's corresponding guards in agent_guard_dict. However, the agent guard dict only gets populated when there's guards in the decision logic (simulator.py: 705, simulator.py: 641). Therefore, when the decision logic is empty, the assertion checks are also not happen.