Lỗi khi tạo class trong C++

E compile ko thấy lỗi gì mà chạy lỗi sợ quá e debug thì thấy đến chỗ tạo class thì nó bị lỗi ạ. ai giúp e với ạ

#include <iomanip>
#include <cstring>
#include <iostream>
using namespace std;

class Monhoc{
      private:
              char* tenMon;
              float diemKT;
              float diemQT;
      public:
             Monhoc();
             Monhoc(const char* tenMon);
             Monhoc(Monhoc& mh);
             ~Monhoc();
             float tinhDiem();
             float getDiemQT();
             void setDiemQT(float diemQT);
             float getDiemKT();
             void setDiemKT(float diemKT);
             char* getTenMon();
             void setTenMon(char* tenMon);
};
Monhoc::Monhoc(){
	tenMon=new char[30];
         tenMon='';
         diemKT=0;
         diemQT=0;
}
Monhoc::Monhoc(const char* tenMon){
	tenMon=new char[30];
         strcpy(this->tenMon,tenMon);
         diemKT=0;
         diemQT=0;
}
Monhoc::Monhoc(Monhoc& mh){
	tenMon=new char[30];
         strcpy(tenMon,mh.tenMon);
         diemKT=mh.diemKT;
         diemQT=mh.diemQT;
}
Monhoc::~Monhoc(){
	delete[] tenMon;
}
float Monhoc::tinhDiem(){
      return diemQT*0.4+diemKT*0.6;
}
float Monhoc::getDiemQT(){
      return diemQT;
}
void Monhoc::setDiemQT(float diemQT){
     this->diemQT=diemQT;
}
float Monhoc::getDiemKT(){
      return diemKT;
}
void Monhoc::setDiemKT(float diemKT){
     this->diemKT=diemKT;
}
char* Monhoc::getTenMon(){
      return tenMon;
}
void Monhoc::setTenMon(char* tenMon){
     strcpy(this->tenMon,tenMon);
}


class SinhVien{
      private:
              int mssv;
              char* ten;
              Monhoc* dsmh;
              int tongSoMH;
              int soMonDaHoc;
      public:
             SinhVien();
             SinhVien(int ms, char* t);
             SinhVien(int ms, char* t, int tongMH, int soMonDaHoc);
             ~SinhVien();
             float tinhDiemTB();
             void addMonHoc(Monhoc& mh);
};
SinhVien::SinhVien(){
	ten=new char[50];
           mssv=0;
           ten='';
           tongSoMH=0;
           int soMonDaHoc=0;
}
SinhVien::SinhVien(int ms, char* t){
	ten=new char[50];
           mssv=ms;
           strcpy(ten,t);
           tongSoMH=0;
           int soMonDaHoc=0;
}
SinhVien::SinhVien(int ms, char* t, int tongMH, int soMonDaHoc=0){
	ten=new char[50];
           mssv=ms;
           strcpy(ten,t);
           tongSoMH=tongMH;
           dsmh=new Monhoc[tongSoMH];
           this->soMonDaHoc=soMonDaHoc;
}
SinhVien:: ~SinhVien(){
           if(tongSoMH>0) delete[] dsmh;
           delete[] ten;
}
float SinhVien::tinhDiemTB(){
    if(soMonDaHoc>0){
    	float tong=0;
	    for(int i=0;i<soMonDaHoc;i++)
	            tong+=dsmh[i].tinhDiem();
	    return tong/soMonDaHoc;
	} else return 0;
}
void SinhVien::addMonHoc(Monhoc& mh){
     if(soMonDaHoc<tongSoMH){
          dsmh[soMonDaHoc].setTenMon(mh.getTenMon());
          dsmh[soMonDaHoc].setDiemQT(mh.getDiemQT());
          dsmh[soMonDaHoc].setDiemKT(mh.getDiemKT());
          soMonDaHoc++;
     } else cout<<"Khong the them mon da hoc cho sinh vien nay do so mon da hoc da bang tong so mon hoc.
";
}

int main(){
    int n;
    SinhVien* sv=new SinhVien[50];
    cout<<"Tong so sinh vien:   ";
    cin>>n;
    for(int i=0;i<n;i++){
            char* ten;
			ten=new char[50];
            int tongMon=0, soMonDaHoc=0, mssv=0;
            cout<<"Nhap thong cho sinh vien "<< i+1<< endl;
            cout<<"	Ten: ";
            fflush(stdin);
            gets(ten);
            cout<<"	MSSV: ";
            cin>>mssv;
            cout<<"	Tong so mon hoc: ";
            cin>>tongMon;
            do{
                cout<<"	So mon da hoc: ";
                cin>>soMonDaHoc;
                if(tongMon<soMonDaHoc) cout<<"So mon da hoc phai <= Tong so mon hoc. Hay nhap lai!
";
            } while(tongMon<soMonDaHoc);
            sv[i]=SinhVien(mssv,ten,tongMon,soMonDaHoc);
            delete[] ten;
            cout<<"	Nhap diem cac mon:
";
            for(int j=0;j<soMonDaHoc;j++){
                    char* tenMH;
					tenMH=new char[30];
                    float diemKT=0, diemQT=0;
                    cout<<"		Mon thu "<<j+1<<endl;
                    cout<<"			Ten: ";
                    fflush(stdin);
                    gets(tenMH);
                    cout<<"			Diem QT: ";
                    cin>>diemQT;
                    cout<<"			Diem KT: ";
                    cin>>diemKT;
                    Monhoc mon;
                    mon.setTenMon(tenMH);
                    mon.setDiemQT(diemQT);
                    mon.setDiemKT(diemKT);
                    sv[i].addMonHoc(mon);
                    delete[] tenMH;
            }
    }
    cout<<"Diem trung binh cua cac sinh vien:
";
    for(int i=0;i<n;i++){
            cout<<"	Sinh vien thu "<< i+1<<": "<< fixed<< left<< setw(4)<< setprecision(2)<< sv[i].tinhDiemTB()<< endl;
    }
    system("pause");
    return 0;
}