kivy: recreate context menu everytime an item is selected

gui/kivy/uix/screens.py

@@ -75,18 +75,16 @@ class CScreen(Factory.Screen):
         self.hide_menu()
 
     def hide_menu(self):
-        if self.context_menu:
+        if self.context_menu is not None:
             self.remove_widget(self.context_menu)
             self.context_menu = None
 
     def show_menu(self, obj):
-        if self.context_menu is None:
+        self.hide_menu()
         self.context_menu = ContextMenu(obj, self.menu_actions)
-        self.remove_widget(self.context_menu)
         self.add_widget(self.context_menu)
 
 
-
 class HistoryScreen(CScreen):
 
     tab = ObjectProperty(None)