fix #1449 : check controllerMetadata is not null

Author: Jason Separovic

lib/kafkaClient.js

@@ -279,7 +279,7 @@ KafkaClient.prototype.getController = function (callback) {
     var controllerId = result[1].clusterMetadata.controllerId;
     var controllerMetadata = result[0][controllerId];
 
-    var broker = this.getBroker(controllerMetadata.host, controllerMetadata.port);
+    broker = controllerMetadata ? this.getBroker(controllerMetadata.host, controllerMetadata.port) : null;
 
     if (!broker || !broker.isConnected()) {
       this.refreshBrokerMetadata();