fix: Fix adding unwanted class 'null'

README.md

@@ -1,10 +1,19 @@
 # Feather
 
+[![Travis branch](https://img.shields.io/travis/colebemis/feather/master.svg?style=flat-square)](https://travis-ci.org/colebemis/feather)
+[![npm](https://img.shields.io/npm/v/feather-icons.svg?style=flat-square)](https://www.npmjs.com/package/feather-icons)
+[![npm](https://img.shields.io/npm/dm/feather-icons.svg?style=flat-square)](https://npm-stat.com/charts.html?package=feather-icons&from=2017-06-01)
+[![Code Climate](https://img.shields.io/codeclimate/github/colebemis/feather.svg?style=flat-square)](https://codeclimate.com/github/colebemis/feather)
+
 ## What is Feather?
 
-Feather is a collection of **simply beautiful open source icons**. Each icon is designed on a 24x24 grid with an emphasis on simplicity, consistency and legibility.
+Feather is a collection of **simply beautiful open source icons**. Each icon is designed on a 24x24 grid with an emphasis on simplicity, consistency and readability.
 
-[feathericons.com](https://feathericons.com)
+**[feathericons.com](https://feathericons.com)**
+
+```
+npm install feather-icons
+```
 
 ## Table of Contents
 

src/replace.js

@@ -41,7 +41,7 @@ function replaceElement(element, options) {
     return;
   }
 
-  const elementClassAttr = element.getAttribute('class');
+  const elementClassAttr = element.getAttribute('class') || '';
   const classNames = (
     options.class ? `${options.class} ${elementClassAttr}` : elementClassAttr
   );