Return value of function which returns null is dereferenced without checking

Defect 100574 (STATIC_C)
Checker NULL_RETURNS (subcategory none)
File: /src/mongo/db/query/index_tag.cpp
Function mongo::<unnamed>::resolveOrPushdowns(mongo::MatchExpression *)
/src/mongo/db/query/index_tag.cpp, line: 232
Assigning: "indexedOr" = null return value from "getIndexedOr".

            MatchExpression* indexedOr = getIndexedOr(andNode);