sundialsJac does not consistently check for null dstate_dt

[mcneish1]

In griddyn/solvers/sundialsInterface.cpp, sundialsJac is allowed to be passed a null dstate_dt. It acknowledges this here and here.

However,

GridDyn/src/griddyn/solvers/sundialsInterface.cpp

Line 462 in cf850ab

NVECTOR_DATA (sd->use_omp, dstate_dt), filterAd, cj, sd->mode);

and

GridDyn/src/griddyn/solvers/sundialsInterface.cpp

Line 471 in cf850ab

NVECTOR_DATA (sd->use_omp, dstate_dt), *a1, cj, sd->mode);

do not check for this, and can segfault. These should have the same nullptr check as above.