Try Catch exception is not catching the unhandled exception

Question

I am building an app within an application called Rhino where it has a button to call this method.

public void AttachPopupToViewportWindow()
{
    _originalBound = Rhino.RhinoDoc.ActiveDoc.Views.ActiveView.Bounds;
    try
    {
        _formWindow = new SW.Win32Window(NativeHandle);
        General._viewportWindow.AddControl(_formWindow);
    }
    catch (System.ComponentModel.Win32Exception ex) 
    {
    }
}

When the method is called repeatedly in a very short time, the NativeHandle cannot be read anymore and it throws an Unhandled Exception.

The NativeHandle represents a IntPtr address to the WPF control.

I tried different ways of bypassing this exception. They all failed to work. Why hasn't the try-catch block catch the exception?