[Windows] Fix crash when setting weekly updates.

It happens due to our wxRadioButtons having 3 options (indexed by 0, 1
and 2) but we trying to get the index 7 (due to want to check every 7
days).

We should still implement something like WinSparkle for Windows.

- Fix #499.

src/wx/guiinit.cpp

@@ -3398,7 +3398,7 @@ bool MainFrame::BindControls()
             // Online Auto Update check frequency
             getrbi("UpdateNever", gopts.onlineupdates, 0);
             getrbi("UpdateDaily", gopts.onlineupdates, 1);
-            getrbi("UpdateWeekly", gopts.onlineupdates, 7);
+            getrbi("UpdateWeekly", gopts.onlineupdates, 2);
 #else
             wxWindowList &children = d->GetChildren();
             std::vector<wxWindow*> forDeletion;