Unhandled exception thrown: read access violation. this was 0x8003B63

hey I am trying to run a program and I get this error:

Exception thrown at 0x004066A0 in INF1010 TP1.exe: 0xC0000005: Access violation reading location 0x0000A0EC. Unhandled exception thrown: read access violation. this was 0xA0CC.

here is my .cpp code I am not sure what is wrong with it

//Constructeurs
    Depense::Depense() {
        titre_ = "";
        montant_ = 0.0;
    }
    Depense::Depense(const string& titre, double montant) {
        titre_ = "titre";
        montant_ = montant;
    }
    string Depense::getTitre() const {
        return titre_;
    }

    double Depense::getMontant() {
        return montant_; //error is here
    }

    void Depense::setTitre(string& titre) {
        titre_ = titre;
    }

    void Depense::setMontant(double montant) {
        montant_ = montant;
    }

sorry if its in french... all of the necessary #include are also in my file

this is the header file that is associated:

class Depense {
public :

// constructeurs par défaut et parametres
Depense();
Depense(const string& titre, double montant );

// methodes d'accès
string getTitre() const;
double getMontant();

//methodes de modifications
void setTitre(string& titre);
void setMontant(double montant);


//methode d'affichage
void afficherDepense();

private :
    string titre_;
    double montant_;

};

Thanks a lot in advance :)