fix bug

gateway/handlers.go

@@ -87,6 +87,7 @@ func (gw *Gateway) handleFiles(msg *config.Message) {
 	for i, f := range msg.Extra["file"] {
 		fi, ok := f.(config.FileInfo)
 		if !ok {
+			fi = config.FileInfo{}
 			mapstructure.Decode(f.(map[string]interface{}), &fi)
 		}
 		ext := filepath.Ext(fi.Name)