WebSearch: fix for 'rhs is of unknown type'

* Fixes an error that was occurring when a new collection has been added
  (and it had NULL in 'reclist' column of collection table). Because of
  that, the intbitset in get_collection_reclist function was initialized with
  None as a parameter and was throwing an exception.
How about fixing this by adding the TypeError in the list of caught errors? (easier to ask for forgiveness than permission)