refactor: check err.code exists before checking if its in a set

Author: mbroadst

lib/core/error.js

@@ -192,7 +192,7 @@ function isNotMasterError(err) {
 }
 
 function isNodeShuttingDownError(err) {
-  return SDAM_NODE_SHUTTING_DOWN_ERROR_CODES.has(err.code);
+  return err.code && SDAM_NODE_SHUTTING_DOWN_ERROR_CODES.has(err.code);
 }
 
 /**

test/functional/connections_stepdown_tests.js

@@ -4,7 +4,9 @@ const chai = require('chai');
 const expect = chai.expect;
 
 function ignoreNsNotFound(err) {
-  if (!err.message.match(/ns not found/)) throw err;
+  if (!err.message.match(/ns not found/)) {
+    throw err;
+  }
 }
 
 function connectionCount(db) {