wxGUI: correctly delete layertree, see https://trac.osgeo.org/grass/ticket/3505

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@72455 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/mapdisp/frame.py

@@ -848,10 +848,9 @@ class MapFrame(SingleMapFrame):
         elif self.page:
             pgnum = self.layerbook.GetPageIndex(self.page)
             if pgnum > -1:
-                self.layerbook.RemovePage(pgnum)
+                self._mgr.UnInit()
+                self.layerbook.DeletePage(pgnum)
         Debug.msg(2, "MapFrame.OnCloseWindow(): function ends")
-        self._mgr.UnInit()
-        self.Destroy()
 
     def Query(self, x, y):
         """Query selected layers.