Control c = Control.FromHandle (hwnd.client_window);
if (c != null) {
Form form = c.FindForm ();
- if (form != null) {
+ if (form != null && !form.IsDisposed) {
Driver.SendMessage (form.Handle, Msg.WM_ACTIVATE, (IntPtr) WindowActiveFlags.WA_ACTIVE, IntPtr.Zero);
XplatUICarbon.ActiveWindow = hwnd.client_window;
}