If you are ever trying to combine two Oracle PL/SQL collections using MULTISET UNION and get an error that looks something like this:

PLS-00801: internal error [*** ASSERT at file pdw4.c, line 2045; Type 0x0A3B7470 has no MAP method.; NEWS_FEEDS__UP__F__103002[7, 5]]

You probably need to run this command on the object type of that data you are merging:
alter type [Item Type Name] add map member function m  return number invalidate/