Powershell crashes, when GridView starts with empty table

Question

I have a very specific issue with a Powershell code which runs a GUI in its own runspace. All works as expected, but if I start showing the below GridView with an empty table, then the process crashes at the point, when he should generate an event that the textbox-text has changed. If I add any row to that table then all works fine again. What could it be? How to fix it?

Here the Code-snippet in question:

# sample script to show a forms-GUI and continue script in parallel

cls
Remove-Variable * -ea 0
$errorActionPreference = 'stop'

# hashtable to exchange data between runspaces:
$ht = [Hashtable]::Synchronized(@{})

# create new runspace for the GUI:
$rs = [RunspaceFactory]::CreateRunspace()
$rs.Name = 'GUI'
$rs.ApartmentState,$rs.ThreadOptions = "STA","ReUseThread"
$rs.Open()
$rs.SessionStateProxy.SetVariable('ht',$ht)

# define the GUI-code for the new runspace:
$cmd = [PowerShell]::Create().AddScript({
    Add-Type -AssemblyName PresentationFramework
    Add-Type -AssemblyName System.Windows.Forms 
    Add-Type -AssemblyName System.Drawing

    $exe = "$env:windir\HelpPane.exe"
    $Icon = [System.Drawing.Icon]::ExtractAssociatedIcon($exe)

    $formWidth  = 600
    $formHeight = 420
    $formCenter = [int]$formWidth/2

    $buttonWidth = 80
    $buttonWidthSmall = 50
    $buttonHeight= 22
    $buttonSpace = 10

    $form = [System.Windows.Forms.Form]::new()
    $form.Text = 'Sample Form'
    $form.Icon = $icon
    $form.MaximizeBox = $false
    $form.MinimizeBox = $false
    $form.Size = @{Width=$formWidth;Height=$formHeight}
    $form.StartPosition = 'CenterScreen'
    $form.FormBorderStyle = 'Fixed3D'

    $OKButton = [System.Windows.Forms.Button]::new()
    $OKButton.Anchor = 'Bottom,Right'
    $OKButton.Text = 'OK'
    $OKButton.Size = @{Width=$buttonWidth;Height=$buttonHeight}
    $OKButton.Location = @{x=$formWidth-$buttonWidth-50; y=$formHeight-$buttonHeight-60}
    $OKButton.DialogResult = 'OK'
    $form.AcceptButton = $OKButton
    $form.Controls.Add($OKButton)

    $cancelButton = [System.Windows.Forms.Button]::new()
    $cancelButton.Anchor = 'Bottom,Left'
    $cancelButton.Text = 'Exit'
    $cancelButton.Size = @{Width=$buttonWidth;Height=$buttonHeight}
    $cancelButton.Location = @{x=30; y=$formHeight-$buttonHeight-60}
    $cancelButton.DialogResult = 'Cancel'
    $form.CancelButton = $cancelButton
    $form.Controls.Add($cancelButton)

    $label = [System.Windows.Forms.Label]::new()
    $label.Text = 'Please type some text here:'
    $label.Location = @{x=20; y=15}
    $label.Size = @{Width=280;Height=20}
    $form.Controls.Add($label)

    $textBox = [System.Windows.Forms.TextBox]::new()
    $textBox.Location = @{x=20; y=40}
    $textBox.Size = @{Width=250;Height=20}
    $textBox.Add_TextChanged({
        # put the new text into the shared queue and trigger event in other runspace:
        $ht.queue.Enqueue($textBox.Text)
        $ht.Host.Runspace.Events.GenerateEvent( "TextChanged", $this, $null, $null)
    })
    $form.Controls.Add($textBox)

    $grid = [System.Windows.Forms.DataGridView]::new()
    $grid.ReadOnly = $true
    $grid.Anchor = 'Top,Bottom,Left,Right'
    $grid.Location = @{x=10;y=80}
    $grid.Size = @{Width=$formWidth-40;Height=$formHeight-180}
    $grid.ScrollBars = 'Both'
    $grid.AutoGenerateColumns = $false
    $grid.AutoResizeColumns()
    $grid.AllowUserToAddRows = $false
    $grid.AllowUserToDeleteRows = $false
    $grid.AutoSizeColumnsMode = 'Fill'
    $grid.AllowUserToResizeRows = $false
    $grid.AutoSizeRowsMode = 'None'
    $grid.SelectionMode = 'FullRowSelect'
    $grid.ColumnHeadersHeightSizeMode = 'DisableResizing'
    $grid.ColumnHeadersDefaultCellStyle.Alignment = 'MiddleCenter'
    $grid.RowHeadersVisible = $false

    foreach($name in @('column-1', 'column-2')){ 
        $cId  = $grid.Columns.Add($name, $name)
        $grid.columns[$cId].DataPropertyName = $name
        $grid.columns[$cId].SortMode = 0
    }
    $grid.Columns['column-1'].FillWeight = 1
    $grid.Columns['column-2'].FillWeight = 1

    $grid.DataSource = $ht.table
    $grid.Add_SelectionChanged({
        $grid.ClearSelection()
    })
    $form.Controls.Add($grid)

    $form.Add_Shown({$textBox.Select()})
    $form.TopMost = $true
    $form.BringToFront()
    $form.Activate()
    $result = $form.ShowDialog()
})

# create a table:
$table = [System.Data.DataTable]::new()
$null = $table.Columns.Add('column-1')
$null = $table.Columns.Add('column-2')

################## if I remove next line, then the process crashes. WHY ??? ################
$null = $table.rows.Add(@('a', 'b'))

# define variables used in both runspaces:
$ht.Host = $host
$ht.table = $table
$ht.queue = [System.Collections.Queue]::new()

# start the GUI in parallel:
$cmd.Runspace = $rs
$handle = $cmd.BeginInvoke()

# (optional) cleanup previous jobs:
$oldJobs = get-job -Name "TextChanged" -ea 0
foreach($j in $oldJobs) {$j.dispose()}

# this needs to run as an event-handler to update the table in parallel while the code continues:
$evt = Register-EngineEvent -SourceIdentifier "TextChanged" -Action {
    while ($ht.queue.Count) {
        $text = $ht.queue.Dequeue()
        $null = $table.rows.Add(@($text, 'b'))
    }
}

# here I want to do a couple of long-lasting routines... 

# wait for end of GUI:
do {
    sleep -Milliseconds 100
} until ($handle.IsCompleted)

# cleanup:
$cmd.Dispose()
$rs.Dispose()
$evt.Dispose()
$table | ft -AutoSize
'done.' 

After some more tests, I can confirm, that this line of code causes the crash in the GUI-runspace:

$null = $ht.table.rows.Add(@($text, 'b'))

and it seems to be related to the fact, that the DataGrid has that shared table as a source. But why does it only crash, when the table is empty? And how to get this fixed?

@mclayton figured out, that if I disable the $grid.ClearSelection() command then its not crashing anymore, but how can I still unselect any selected row? Especially the first one?