ListBox: fix possible unexpected acquisition

The use case is a listbox method being called for a document A
and returning objects that:
- aren't children of A
- but wrapped with `.__of__(A)`

By using `aq_self` instead of `aq_base`, the listbox could still
acquire from the real parent of the returned object and wrongly access
an attribute directly (e.g. comment) instead of using an appropriate
method (if there's no `comment` attribute, getComment returns '').

See merge request nexedi/erp5!1820

product/ERP5Form/ListBox.py

@@ -2336,7 +2336,7 @@ class ListBoxRendererLine:
 
         # If a tales expression is not defined, get a skin, an accessor or a property.
         if not tales:
-          if getattr(aq_self(brain), alias, None) is not None:
+          if getattr(aq_base(brain), alias, brain) is not brain:
             original_value = getattr(brain, alias)
           else:
             # Get the trailing part.