Preprocessor: fix crash when no computational task is required

preprocessor/DynamicModel.cc

@@ -2683,6 +2683,8 @@ DynamicModel::computingPass(bool jacobianExo, bool hessian, bool thirdDerivative
 {
   assert(jacobianExo || !(hessian || thirdDerivatives || paramsDerivatives));
 
+  initializeVariablesAndEquations();
+  
   // Prepare for derivation
   computeDerivIDs();
 

preprocessor/ModFile.cc

@@ -358,7 +358,6 @@ ModFile::computingPass(bool no_tmp_terms)
       dynamic_model.toStatic(static_model);
       if (!no_static)
         {
-          static_model.initializeVariablesAndEquations();
           if (mod_file_struct.stoch_simul_present
               || mod_file_struct.estimation_present || mod_file_struct.osr_present
               || mod_file_struct.ramsey_policy_present || mod_file_struct.identification_present)
@@ -371,7 +370,6 @@ ModFile::computingPass(bool no_tmp_terms)
           || mod_file_struct.estimation_present || mod_file_struct.osr_present
           || mod_file_struct.ramsey_policy_present || mod_file_struct.identification_present)
         {
-          dynamic_model.initializeVariablesAndEquations();
           if (mod_file_struct.simul_present)
             dynamic_model.computingPass(true, false, false, false, global_eval_context, no_tmp_terms, block, use_dll, byte_code);
           else

preprocessor/StaticModel.cc

@@ -1065,6 +1065,8 @@ StaticModel::collect_first_order_derivatives_endogenous()
 void
 StaticModel::computingPass(const eval_context_t &eval_context, bool no_tmp_terms, bool hessian, bool block, bool bytecode)
 {
+  initializeVariablesAndEquations();
+
   // Compute derivatives w.r. to all endogenous, and possibly exogenous and exogenous deterministic
   set<int> vars;