Window with Gecko WebControl does not reopen

I have a window A which contains a button which opens a new window B containing a WebControl. Each time the button in window A is pressed a new instance of window B opens with a different URL exposed in the B WebControl. This works fine repeatedly with new windows provided at least one child window remains open.

As soon as all child windows have been closed then a press on the button in window A crashes the application with the following stacktrace when the method ShowAll() is applied to the window:


  at (wrapper managed-to-native) Gtk.Widget.gtk_widget_show_all (intptr) <0x00004>
  at (wrapper managed-to-native) Gtk.Widget.gtk_widget_show_all (intptr) <0xffffffff>
  at Gtk.Widget.ShowAll () [0x00000] in /usr/src/packages/BUILD/gtk-sharp-2.12.1/gtk/generated/Widget.cs:6228
  at reports.report.rpt (string) [0x00153] in /home/colin/mobo/mobo/reports.cs:101
.....

I can put in a check that at least one window remains, but I am wondering if I am missing something else important?