Minor fix in componentDidMount

Author: fakenickels

lib/index.js

@@ -21,9 +21,10 @@ const Img = React.createClass({
     const holder = ReactDOM.findDOMNode(this);
 
     if(!holder) return;
+    const intended = holder.querySelector(`.${styles['intended']}`);
+    if(!intended) return;
 
-    holder.querySelector(`.${styles['intended']}`)
-    .addEventListener('load', () => {
+    intended.addEventListener('load', () => {
       holder.querySelector(`.${styles['placeholder']}`)
         .classList.add(styles['deactivated']);
     });