Return value of function which returns null is dereferenced without checking

Defect 105017 (STATIC_C)
Checker NULL_RETURNS (subcategory none)
File: /src/mongo/db/s/txn_two_phase_commit_cmds.cpp
Function mongo::<unnamed>::CoordinateCommitTransactionCmd::Invocation::typedRun(mongo::OperationContext *)
/src/mongo/db/s/txn_two_phase_commit_cmds.cpp, line: 269
Assigning: "txnParticipant" = null return value from "get".

                    auto txnParticipant = TransactionParticipant::get(opCtx);

File: /src/mongo/db/s/txn_two_phase_commit_cmds.cpp
Function mongo::<unnamed>::CoordinateCommitTransactionCmd::Invocation::typedRun(mongo::OperationContext *)
/src/mongo/db/s/txn_two_phase_commit_cmds.cpp, line: 269
Assigning: "txnParticipant" = null return value from "get".

                    auto txnParticipant = TransactionParticipant::get(opCtx);