Add Blank (Empty) Row to BindingSource in VB.Net

Dear sir,

I'm trying to add a Row DataGridView with Event Button in VB.NET

But I want to add a row after the 3 columns are filled, I try the code below there is an error `Object reference not set to an instance of an object.` in button1 event

Please guide me

Thanks

Public Class Form1
    Private BindingSource1 As BindingSource = Nothing
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        'Hide the last blank line.
        DataGridView1.AllowUserToAddRows = False
        'Clear Columns.
        DataGridView1.Columns.Clear()
 
        'Add Columns.
        Dim customerId As DataGridViewColumn = New DataGridViewTextBoxColumn()
        customerId.Name = "CustomerId"
        customerId.HeaderText = "CustomerId Id"
        customerId.DataPropertyName = "CustomerId"
        customerId.Width = 100
        DataGridView1.Columns.Insert(0, customerId)
 
        Dim name As DataGridViewColumn = New DataGridViewTextBoxColumn()
        name.HeaderText = "Name"
        name.Name = "Name"
        name.DataPropertyName = "Name"
        name.Width = 100
        DataGridView1.Columns.Insert(1, name)
 
        Dim country As DataGridViewColumn = New DataGridViewTextBoxColumn()
        country.Name = "Country"
        country.HeaderText = "Country"
        country.DataPropertyName = "Country"
        country.Width = 100
        DataGridView1.Columns.Insert(2, country)
 
        'Bind the DataGridView.
        Dim dt As DataTable = New DataTable()
        dt.Columns.AddRange(New DataColumn(2) {New DataColumn("CustomerId"), New DataColumn("Name"), New DataColumn("Country")})
        BindingSource1 = New BindingSource With {.DataSource = dt}
        DataGridView1.DataSource = BindingSource1
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        `error below line code
        If Not String.IsNullOrEmpty(DataGridView1.CurrentRow.Cells("CustomerId").Value?.ToString()) And Not String.IsNullOrEmpty(DataGridView1.CurrentRow.Cells("Name").Value?.ToString()) And Not String.IsNullOrEmpty(DataGridView1.CurrentRow.Cells("Country").Value?.ToString()) Then
            BindingSource1.AddNew()
        End If
 
    End Sub
End Class

at the time of form load there is no row blank at all because I use

DataGridView1.AllowUserToAddRows = False

How did I add a row blank first and Prevent insert more blank row if there blank row already? (when button1 is click) and then if the cells of the 3 columns are filled then I can add row blank.