to be sure: z3model by const reference

src/storm/solver/Z3SmtSolver.cpp

@@ -7,7 +7,7 @@
 namespace storm {
 	namespace solver {
 #ifdef STORM_HAVE_Z3
-		Z3SmtSolver::Z3ModelReference::Z3ModelReference(storm::expressions::ExpressionManager const& manager, z3::model model, storm::adapters::Z3ExpressionAdapter& expressionAdapter) : ModelReference(manager), model(model), expressionAdapter(expressionAdapter) {
+		Z3SmtSolver::Z3ModelReference::Z3ModelReference(storm::expressions::ExpressionManager const& manager, z3::model const& model, storm::adapters::Z3ExpressionAdapter& expressionAdapter) : ModelReference(manager), model(model), expressionAdapter(expressionAdapter) {
             // Intentionally left empty.
 		}
 #endif

src/storm/solver/Z3SmtSolver.h

@@ -17,7 +17,7 @@ namespace storm {
 			class Z3ModelReference : public SmtSolver::ModelReference {
 			public:
 #ifdef STORM_HAVE_Z3
-				Z3ModelReference(storm::expressions::ExpressionManager const& manager, z3::model m, storm::adapters::Z3ExpressionAdapter& expressionAdapter);
+				Z3ModelReference(storm::expressions::ExpressionManager const& manager, z3::model const& m, storm::adapters::Z3ExpressionAdapter& expressionAdapter);
 #endif
                 virtual bool getBooleanValue(storm::expressions::Variable const& variable) const override;
                 virtual int_fast64_t getIntegerValue(storm::expressions::Variable const& variable) const override;