It's valid to pass wxNOT_FOUND to SetSelection in order to clear selections.

Avoid assert and erroneous setting of -1.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41729 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/listbox.cpp

@@ -942,6 +942,7 @@ void wxListBox::DoSetSelection( int n, bool select )
     {
         // ... and not generate any events in the process
         GtkDeselectAll();
+	return;
     }
 
     wxCHECK_RET( IsValid(n), wxT("invalid index in wxListBox::SetSelection") );