Fix potentially incorrect disabling of Newton's method by `SteadyStat…

…eSensitivityMode::integrationOnly`

Fixes a bug that would result in disabling Newton's method for
steady-state computation when steady-state sensitivity mode is set
to `integrationOnly`, even if no senitivities are computed.

This was because only the sensitivity method was checked, but not the sensitivity order.

Fixes AMICI-dev#2575.

src/steadystateproblem.cpp

@@ -133,7 +133,8 @@ void SteadystateProblem::findSteadyState(
         = model.getSteadyStateComputationMode()
               == SteadyStateComputationMode::integrationOnly
           || solver.getNewtonMaxSteps() == 0
-          || (model.getSteadyStateSensitivityMode()
+          || (solver.getSensitivityOrder() >= SensitivityOrder::first
+              && model.getSteadyStateSensitivityMode()
                   == SteadyStateSensitivityMode::integrationOnly
               && ((it == -1
                    && solver.getSensitivityMethodPreequilibration()