Помогите с отладкой программы в vb

Имеются два класса в VB:
Первый родительский:

Code:

Imports System.IO
Public Class Ставки
    Private fs As String 'путь до файла +
    Protected Friend fstav(,) As String 'ставки +
    Private Shared fpob As String 'список победителей +
    Private fn As Integer 'кол-во ставок +
    Private Shared fsum As String ' призовой фонд  +
    Private fofd As OpenFileDialog
    Dim f As Boolean = True 'просто флаг
    Dim k As Integer 'счетчик
    Public Sub New()
    End Sub
    Public Sub New(ByVal n As Integer)
        ReDim fstav(n - 1, 3)
    End Sub
    Public Property ofd() As OpenFileDialog
        Get
            Return fofd
        End Get
        Set(ByVal value As OpenFileDialog)
            fofd = value
        End Set
    End Property
    Public Property s() As String
        Get
            Return fs
        End Get
        Set(ByVal value As String)
            fs = value
        End Set
    End Property
    Public Property pob() As String
        Get
            Return fpob
        End Get
        Set(ByVal value As String)
            For i = 0 To value.Length - 1
                If value.Substring(i, 1) = Space(1) Then k = k + 1
            Next
            If k = 3 Then
                fpob = value
                k = 0
            Else
                MsgBox("Неверно введены победители, установка победителей: 1 2 3")
                fpob = "1 2 3"
                k = 0
            End If
        End Set
    End Property
    Public Property sum() As String
        Get
            Return fsum
        End Get
        Set(ByVal value As String)
            For i = 0 To value.Length - 1
                If Char.IsDigit(value, i) = False Then f = False
            Next
            If f = True Then
                fsum = value
            Else
                f = True
                MsgBox("Неверно введен призовой фонд, уставновка фонда на: 1000")
                fsum = CStr(1000)
            End If
        End Set
    End Property
    Public Property n() As Integer
        Get
            Return fn
        End Get
        Set(ByVal value As Integer)
            For i = 0 To CStr(value).Length - 1
                If Char.IsDigit(CStr(value), i) = False Then f = False
            Next
            If f = True Then
                fn = value
            Else
                f = True
                MsgBox("Неверно введен призовой фонд, уставновка фонда на: 1000")
                End
            End If
            fn = value
        End Set
    End Property

    Public Property stav() As String(,)
        Get
            Return fstav
        End Get
        Set(ByVal value(,) As String)
            fstav = value

        End Set
    End Property
    Public Sub readpath(ByVal ofd As OpenFileDialog, ByRef s As String)
        ofd.Filter = "Textfiles(*.txt)|*txt"
        ofd.ShowDialog()
        s = ofd.FileName
    End Sub

    Public Sub read(ByVal s As String, ByVal z As Integer, ByRef stav(,) As String)
        Dim f = New StreamReader(s)
        Dim line, p() As String
        Dim k As Integer = 0
        ReDim stav(z - 1, 3)
        s = "C:\Users\Воробьев\Desktop\1.txt"
        Do While Not (f.EndOfStream)
            line = f.ReadLine()
            p = Split(line, " ")
            For i = 0 To UBound(p)
                stav(k, i) = p(i)
            Next
            k = k + 1
        Loop
        f.Close()
    End Sub
    Public Sub readtb(ByVal tb As TextBox, ByRef o As String)
        o = tb.Text
    End Sub
    Public Sub vivodtb(ByVal tb As TextBox, ByVal stav(,) As String)
        Dim str As String
        For i = 0 To stav.GetLength(0) - 1
            For j = 0 To stav.GetLength(1) - 1
                str = str + stav(i, j) + Space(4)
            Next
            str = str + vbNewLine
        Next
        tb.Text = str
    End Sub
    Sub vivodtb(ByVal tb As TextBox, ByVal k As String)
        tb.Text = k
    End Sub
End Class

И второй, который "дочерний" от него:

Code:

Option Explicit On
Public Class rez
    Inherits Ставки
    Private fstr As String
    Private fotv As Single
    Public Sub New()
    End Sub
    Public Sub New(ByVal n As Integer)
        ReDim Preserve stav(n - 1, 2)
    End Sub

  
    Public Property str() As String
        Get
            Return fstr
        End Get
        Set(ByVal value As String)
            fstr = value
        End Set
    End Property
    Public Property otv() As Single
        Get
            Return fotv
        End Get
        Set(ByVal value As Single)
            fotv = value
        End Set
    End Property

    Public Sub sravn(ByRef gr As Ставки)
        Dim o() As String
        Dim flag As Boolean
        Dim k As Integer = 0
        o = Split(gr.pob, " ")
        For i = 0 To gr.stav.GetLength(0) - 1
            flag = True
            For j = 0 To gr.stav.GetLength(1) - 2
                If o(j) <> gr.stav(i, j) Then flag = False
            Next
            If flag = True Then
                k = k + 1
                str = str + CStr(i + 1) + vbNewLine
            End If
        Next

        If k = 0 Then
            otv = "0"
        Else
            otv = (CInt(sum) / k)
        End If
    End Sub
End Class

Вызов из тела программы:

Code:

    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        g2 = New rez(Form1.g.n)
        g2.sravn(Form1.g)
    End Sub

Компиляция проходит без проблем, но при работе возникает ошибка:
В экземпляре объекта не задана ссылка на объект.

Во втором классе в процедуре sravn в строке For i = 0 To gr.stav.GetLength(0) - 1

Делал проверку массива на значение null получил ответ true, Как можно Это исправить? Заранее спасибо!