Merge pull request matplotlib#8119 from anntzer/drop-None-container-children

Drop None from Container.get_children().

Author: NelleV

lib/matplotlib/container.py

@@ -32,9 +32,8 @@ def set_remove_method(self, f):
         self._remove_method = f
 
     def remove(self):
-        for c in cbook.flatten(self,
-                               scalarp=lambda x: isinstance(x,
-                                                            martist.Artist)):
+        for c in cbook.flatten(
+                self, scalarp=lambda x: isinstance(x, martist.Artist)):
             c.remove()
 
         if self._remove_method:
@@ -102,7 +101,7 @@ def pchanged(self):
             func(self)
 
     def get_children(self):
-        return list(cbook.flatten(self))
+        return [child for child in cbook.flatten(self) if child is not None]
 
 
 class BarContainer(Container):