wxGUI/mapswipe: fix wx.CheckListBox widget wxPyDeprecationWarning (#773)

gui/wxpython/gui_core/simplelmgr.py

@@ -177,7 +177,7 @@ class SimpleLayerManager(wx.Panel):
 
     def OnLayerChecked(self, event):
         """Layer was (un)checked, update layer's info."""
-        checkedIdxs = self._checkList.GetChecked()
+        checkedIdxs = self._checkList.GetCheckedItems()
         for i, layer in enumerate(self._layerList):
             if i in checkedIdxs and not layer.IsActive():
                 layer.Activate()