"Cannot read property 'message' of undefined" error from connect

Since upgrading to v3.2.4, we started seeing occasional fatal errors from `connect`. It seems that a recent change is to blame. The error is thrown from line 287 there whenever `err` has no `message` property (as it wouldn't when, for example, the assignment `err = true` executes three lines prior).

 

mongos> db.isMaster()
{
"ismaster" : true,
"msg" : "isdbgrid",
"maxBsonObjectSize" : 16777216,
"maxMessageSizeBytes" : 48000000,
"maxWriteBatchSize" : 100000,
"localTime" : ISODate("2019-05-13T21:53:26.577Z"),
"logicalSessionTimeoutMinutes" : 30,
"maxWireVersion" : 6,
"minWireVersion" : 0,
"ok" : 1,
"operationTime" : Timestamp(1557784406, 406),
"$clusterTime" : {
"clusterTime" : Timestamp(1557784406, 406),
"signature" :

{ "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) }

}
}