SimulationProblem: Skip or raise Exception when setting NaN as initial state

[SGeeversAtVortech]

In GitLab by @vreeken on Jan 25, 2019, 15:00

Since ed4412c we skip setting NaNs as initial state in optimization problems. There is now a discrepancy between how NaNs in initial state are handled between simulation and optimization, as the former will typically just crash somewhere in CasADi on a NaN check and the latter will work "just fine".

Related to !1089