Return value of function which returns null is dereferenced without checking

Defect 73708 (STATIC_C)
Checker NULL_RETURNS (subcategory none)
File: /src/mongo/db/repair_database.cpp
Function mongo::repairDatabase(mongo::OperationContext *, mongo::StorageEngine *, const std::basic_string<char, std::char_traits<char>, std::allocator<char>>&, bool, bool)::[lambda() (instance 1)]::operator ()() const
/src/mongo/db/repair_database.cpp, line: 227
Assigning: "collection" = null return value from "getCollection".

                    auto collection = db->getCollection(collectionName);