Account for a parent not being adaptable in ITreeBase.iterancestors()

cubicweb_seda/entities/itree.py

@@ -68,6 +68,8 @@ class IContainedToITreeBase(EntityAdapter):
                     break
                 yield curr
                 curr = curr.cw_adapt_to('ITreeBase')
+                if curr is None:
+                    break
         return _uptoroot(self)
 
     iterparents = iterancestors  # Compat. with CubicWeb's ITree.