在datagridview中单击标题时出现System.NullReferenceException

Question

我有一个datagridview，当我点击一个标题进行排序时，我得到以下错误，我无法弄清楚为什么。你们有什么想法我会得到以下错误吗？

Firearm Asset Management Studio.exe中出现“System.NullReferenceException”类型的异常，但未在用户代码中处理

private void firearmView_SelectionChanged(object sender, EventArgs e)
    {          
        if (firearmView.SelectedRows.Count >= 0)
            {
                //Error above is found on the line directly below.
                serialLabel.Text = firearmView.CurrentRow.Cells[0].Value.ToString();
                manLabel.Text = firearmView.CurrentRow.Cells[1].Value.ToString();
                modelLabel.Text = firearmView.CurrentRow.Cells[2].Value.ToString();
                caliberLabel.Text = firearmView.CurrentRow.Cells[3].Value.ToString();
                actionLabel.Text = firearmView.CurrentRow.Cells[4].Value.ToString();
                priceLabel.Text = firearmView.CurrentRow.Cells[5].Value.ToString();
                dataLabel.Text = firearmView.CurrentRow.Cells[6].Value.ToString();
                sellLabel.Text = firearmView.CurrentRow.Cells[7].Value.ToString();
                locationLabel.Text = firearmView.CurrentRow.Cells[8].Value.ToString();
                ownerLabel.Text = firearmView.CurrentRow.Cells[9].Value.ToString();
                valueLabel.Text = firearmView.CurrentRow.Cells[10].Value.ToString();
                notesLabel.Text = firearmView.CurrentRow.Cells[11].Value.ToString();
            }
     }