Handle err in queue_proxy

Found on lgtm.com

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

gateway/handlers/queue_proxy.go

@@ -43,6 +43,10 @@ func MakeQueuedProxy(metrics metrics.MetricOptions, queuer queue.RequestQueuer,
 		name := vars["name"]
 
 		queueName, err := getQueueName(name, functionQuery)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
 
 		req := &queue.Request{
 			Function:    name,