stoch_simul: handle case where hessian was not computed by the preprocessor

occurs when .mod file was run outside of the GUI and order was set to 1 in one of the computation commands

src/gui_stoch_simulation.m

@@ -217,6 +217,9 @@ uicontrol( ...
             backup = gui_auxiliary.backup_options(options_);
             options_ = default_option_values(M_);
             options_ = gui_auxiliary.add_backup_to_options(options_, backup);
+            if ~isfield(M_, 'hessian_eq_zero')
+                options_.order = 1;
+            end
             if any([handles.shocksTable.Data{:,1}])
                 options_.irf_shocks = char(handles.shocksTable.Data([handles.shocksTable.Data{:,1}],2));
             end