No longer report momemts in stoch_simul with order>=3 if periods not specified

Previously Dynare was reporting dummy theoretical moments

matlab/stoch_simul.m

@@ -138,7 +138,10 @@ if options_.nomoments == 0
     if PI_PCL_solver
         PCL_Part_info_moments (0, PCL_varobs, oo_.dr, i_var);
     elseif options_.periods == 0
-        disp_th_moments(oo_.dr,var_list);
+        % There is no code for theoretical moments at 3rd order
+        if options_.order <= 2
+            disp_th_moments(oo_.dr,var_list);
+        end
     else
         disp_moments(oo_.endo_simul,var_list);
     end

matlab/th_autocovariances.m

@@ -45,6 +45,10 @@ if nargin<5
     nodecomposition = 0;
 end
 
+if options_.order >= 3
+    error('Theoretical moments not implemented above 2nd order')
+end
+
 endo_nbr = M_.endo_nbr;
 exo_names_orig_ord  = M_.exo_names_orig_ord;
 if exist('OCTAVE_VERSION')