typo in CHANGES.txt

doc/CHANGES.txt

@@ -12,7 +12,7 @@ Zope Changes
       - Collector #2235: A number of ZCatalog methods were doing boolean
         evaluation of objects that implemented __len__ instead of checking
         them against None. Replaced a number of "if not obj" with
-        "if obj is not None".
+        "if obj is None".
 
       - Collector #2218: fixed wrong logger argument in OFS/Cache.py