I created a class called Matrix with a 2d array. I can run it with the constructor, copy constructor and destructor. When I introduce the unary negation operator, I get a runtime error

Driver

#include<iostream>
#include"Matrix.h"
using namespace std;
void main()
{
	Matrix m(4, 5);
	Matrix m2(m);
	m2.setValue(1,2,12);
	int x;
	m2.getValue(1,2,x);
	Matrix m3;
	m3 = -m2;

}

Header

#ifndef MATRIX_H
#define MATRIX_H
class Matrix
{
public:
	Matrix(int rSize=3, int cSize=3);
	Matrix(const Matrix& m);
	~Matrix();
	bool setValue(int rSize, int cSize, int value);
	bool getValue(int rVal, int cVal, int& value)const;
	const Matrix& operator- ();
private:
	int rowSize;
	int columnSize;
	int** arr;
};
#endif

Source

#include<iostream>
#include"Matrix.h"
using namespace std;
Matrix::Matrix(int rSize,int cSize)
{
	columnSize = cSize;
	rowSize = rSize;
	arr = new int* [rowSize];
	for(int i=0; i<rowSize; i++)
		arr[i] = new int[columnSize];
	for(int j=0; j<rowSize; j++)
	{
		for(int k=0; k<columnSize; k++)
			arr[j][k] = 0;
	}

}
Matrix::Matrix(const Matrix& m)
{
	columnSize = m.columnSize;
	rowSize = m.rowSize;
	arr = new int* [rowSize];
	for(int i=0; i<rowSize; i++)
	{
		arr[i] = new int [columnSize];
	}
	for(int i=0; i<rowSize; i++)
	{
		for(int j=0; j<columnSize; j++)
			arr[i][j] = m.arr[i][j];
	}
}
Matrix::~Matrix()
{
	for(int i = 0; i < rowSize; ++i)
		delete [] arr[i];
	delete [] arr;
}
bool Matrix::setValue(int rVal, int cVal, int value)
{
	if((rVal<0)||(cVal<0)||(rVal>rowSize-1)||(cVal>columnSize-1))
		return false;
	arr[rVal][cVal] = value;
	return true;
}
bool Matrix::getValue(int rVal, int cVal, int& value)const
{
	if((rVal<0)||(cVal<0)||(rVal>rowSize-1)||(cVal>columnSize-1))
		return false;
	value = arr[rVal][cVal];
	return true;
}
const Matrix& Matrix:: operator- ()
{
	Matrix m(*this);
	for (int i = 0; i< rowSize; i++)
	{
		for(int j=0; j<columnSize; j++)
			m.arr[i][j] = (this->arr[i][j])* -1 ;
	}
	return m;
}