fix(NODE-3192): check clusterTime is defined before access (#2806)

Author: nbbeeken

lib/core/wireprotocol/command.js

@@ -45,14 +45,19 @@ function _command(server, ns, cmd, options, callback) {
   const shouldUseOpMsg = supportsOpMsg(server);
   const session = options.session;
 
-  let clusterTime = server.clusterTime;
+  const serverClusterTime = server.clusterTime;
+  let clusterTime = serverClusterTime;
   let finalCmd = Object.assign({}, cmd);
   if (hasSessionSupport(server) && session) {
+    const sessionClusterTime = session.clusterTime;
     if (
-      session.clusterTime &&
-      session.clusterTime.clusterTime.greaterThan(clusterTime.clusterTime)
+      serverClusterTime &&
+      serverClusterTime.clusterTime &&
+      sessionClusterTime &&
+      sessionClusterTime.clusterTime &&
+      sessionClusterTime.clusterTime.greaterThan(serverClusterTime.clusterTime)
     ) {
-      clusterTime = session.clusterTime;
+      clusterTime = sessionClusterTime;
     }
 
     const err = applySession(session, finalCmd, options);
@@ -61,8 +66,8 @@ function _command(server, ns, cmd, options, callback) {
     }
   }
 
-  // if we have a known cluster time, gossip it
   if (clusterTime) {
+    // if we have a known cluster time, gossip it
     finalCmd.$clusterTime = clusterTime;
   }