Fixed problem of ZCatalog instantiation with no container and no vocab_id.

lib/python/Products/ZCatalog/ZCatalog.py

@@ -224,8 +224,11 @@ class ZCatalog(Folder, Persistent, Implicit):
     _v_transaction = None
     
     def __init__(self, id, title='', vocab_id=None, container=None):
-        self=self.__of__(container)
-        
+        if vocab_id is not None and container is None:
+            raise CatalogError, ("You cannot specify a vocab_id without "
+                                     "also specifying a container.")
+        if container is not None:
+            self=self.__of__(container)
         self.id=id
         self.title=title