Return value of function which returns null is dereferenced without checking

Defect 104958 (STATIC_C)
Checker NULL_RETURNS (subcategory none)
File: /src/mongo/db/ops/write_ops_exec.cpp
Function mongo::performDeletes(mongo::OperationContext *, const mongo::write_ops::Delete &)
/src/mongo/db/ops/write_ops_exec.cpp, line: 835
Assigning: "txnParticipant" = null return value from "get".

        auto txnParticipant = TransactionParticipant::get(opCtx);