Exception Thrown (C++)

After running the following .cpp file within Visual Studios, I receive the following error: Exception thrown at 0x0074425E in HomeWork3.exe: 0xC0000005: Access violation reading location 0x00000000.

The error comes from the following slew of code:

int Table::getData(int r, int c) const {
    return columns[r]->getData(c);
};

The entire code is as follows:

//Table.cpp
    #include <cstdlib>
    #include "Table.h"
    Table::Table(unsigned int r, unsigned int c) {

        szRow = r;
        szCol = c;

        columns = new RowAray*[r];

        for (int i = 0; i < r; i++) {
            columns[i] = new RowAray(c);
        }

        for (int i = 0; i < r; i++) {
            for (int j = 0; j < c; j++) {
                columns[i]->setData(j, (rand() % 90 + 10));
            }
        }
    }

    Table::~Table() {
        for (int i = 0; i < szRow; i++) {
            columns[i] = 0;
            delete[] columns[i];
        }
        columns = 0;
        delete[] columns;
    }

    Table::Table(const Table &t) {
        szRow = t.szRow;
        szCol = t.szCol;
        columns = t.columns;
    };

    int Table::getData(int r, int c) const {
        return columns[r]->getData(c);
    };

    void Table::setData(int r, int c, int value) {
        columns[r]->setData(c, value);
    }

//main.cpp

 //User Libraries
    #include <cstdlib>
    #include <ctime>
    #include <iostream>
    #include <iomanip>
    using namespace std;

    //User Libraries
    #include "PlusTab.h"
    //Global Constants

    //Function Prototype
    void prntTab(const Table &);

    //Execution Begins Here!
    int main(int argc, char** argv) {
        //Initialize the random seed
        srand(static_cast<unsigned int>(time(0)));

        //Declare Variables
        int rows = 3, cols = 4;

        //Test out the Tables
        PlusTab tab1(rows, cols);
        PlusTab tab2(tab1);
        PlusTab tab3 = tab1 + tab2;

        //Print the tables
        cout << "Abstracted and Polymorphic Print Table 1 size is [row,col] = ["
            << rows << "," << cols << "]";
        prntTab(tab1);
        cout << "Copy Constructed Table 2 size is [row,col] = ["
            << rows << "," << cols << "]";
        prntTab(tab2);
        cout << "Operator Overloaded Table 3 size is [row,col] = ["
            << rows << "," << cols << "]";
        prntTab(tab3);

        //Exit Stage Right
        system("pause");
        return 0;
    }

    void prntTab(const Table &a) {
        cout << endl;
        for (int row = 0; row<a.getSzRow(); row++) {
            for (int col = 0; col<a.getSzCol(); col++) {
                cout << setw(4) << a.getData(row, col);
            }
            cout << endl;
        }
        cout << endl;
    }

//RowAray.cpp

#include <cstdlib>
#include "RowAray.h"

RowAray::RowAray(unsigned int n)
{
    this->size = n;
    rowData = new int[n];
}

RowAray::~RowAray()
{
    delete[]rowData;
}

void RowAray::setData(int i, int r)
{
    this->rowData[i] = r;
}

//Table.h

#ifndef TABLE_H
#define TABLE_H

#include "AbsTabl.h"

class Table :public AbsTabl {
public:
    Table(unsigned int, unsigned int);
    Table(const Table &);
    virtual ~Table();
    int getSzRow()const { return szRow; }
    int getSzCol()const { return szCol; }
    int getData(int, int)const;
    void setData(int, int, int);
};

#endif /* TABLE_H */

//AbsRow.h

#ifndef ABSROW_H
#define ABSROW_H

class AbsRow {
protected:
    int size;
    int *rowData;
public:
    virtual int getSize()const = 0;
    virtual int getData(int)const = 0;
};

#endif /* ABSROW_H */

//AbsTabl.h

#ifndef ABSTABL_H
#define ABSTABL_H

#include "RowAray.h"

class AbsTabl {
protected:
    int szRow;
    int szCol;
    RowAray **columns;
public:
    virtual int getSzRow()const = 0;
    virtual int getSzCol()const = 0;
    virtual int getData(int, int)const = 0;
};

#endif /* ABSTABL_H */

//PlusTabl.h

#ifndef PLUSTAB_H
#define PLUSTAB_H

#include "Table.h"

class PlusTab :public Table {
public:
    PlusTab(unsigned int r, unsigned int c) :Table(r, c) {};
    PlusTab operator+(const PlusTab &t);
};

#endif /* PLUSTAB_H */

//RowAray.h

#ifndef ROWARAY_H
#define ROWARAY_H

#include "AbsRow.h"

class RowAray :public AbsRow {
public:
    RowAray(unsigned int);
    virtual ~RowAray();
    int getSize()const { return size; }
    int getData(int i)const {
        if (i >= 0 && i<size)return rowData[i];
        else return 0;
    }
    void setData(int, int);
};

#endif /* ROWARAY_H */

//PlusTab.cpp

#include "PlusTab.h"

PlusTab PlusTab::operator+(const PlusTab &t) {
    PlusTab tab(this->getSzRow(), this->getSzCol());

    for (int i = 0; i < tab.getSzRow(); i++) {
        for (int j = 0; j <tab.getSzCol(); j++) {
            (tab.columns[i])->setData(j, this->getData(i, j) + t.getData(i, j));
        }
    }
    return tab;
}

I am not sure why this is happening.