This is reported at https://gna.org/bugs/?22257.
This is a recurring problem in Mac OS X as it cannot be tested in the relax test suite. The problem
is with wxPython. The modal dialogs, such as the free file format window, cannot be destroyed on
Mac OS X using wx.Dialog.Destroy() - this kills wxPython and hence kills relax. The problem does
not exist on any other operating system. To fix this, all wx.Dialog.Destroy() calls have been
replaced with wx.Dialog.Close().
