Fix preferences dialog

gui/mainFrame.py

@@ -371,7 +371,6 @@ class MainFrame(wx.Frame):
     def showPreferenceDialog(self, event):
         dlg = PreferenceDialog(self)
         dlg.ShowModal()
-        dlg.Destroy()
 
     def goWiki(self, event):
         wx.LaunchDefaultBrowser('https://github.com/DarkFenX/Pyfa/wiki')

gui/preferenceDialog.py

@@ -77,4 +77,4 @@ class PreferenceDialog(wx.Dialog):
         self.btnOK.Bind(wx.EVT_BUTTON, self.OnBtnOK)
 
     def OnBtnOK(self, event):
-        self.Destroy()
+        self.Close()