chore: add missing copyright and update if/else (#1497)

render/reader.go

@@ -1,3 +1,7 @@
+// Copyright 2018 Gin Core Team.  All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
 package render
 
 import (

render/text.go

@@ -30,7 +30,7 @@ func WriteString(w http.ResponseWriter, format string, data []interface{}) {
 	writeContentType(w, plainContentType)
 	if len(data) > 0 {
 		fmt.Fprintf(w, format, data...)
-	} else {
+		return
+	}
 	io.WriteString(w, format)
 }
-}