[repl] add error handling for async scope fetching

lib/repl.js

@@ -405,7 +405,9 @@ REPLServer.prototype.complete = function(line, callback) {
           completionGroupsLoaded();
         } else {
           this.eval('.scope', this.context, 'repl', function(err, globals) {
-            if (Array.isArray(globals[0])) {
+            if (err || !globals) {
+              addStandardGlobals();
+            } else if (Array.isArray(globals[0])) {
               // Add grouped globals
               globals.forEach(function(group) {
                 completionGroups.push(group);