From 98a33ae6978a78c69f59027cef2a202b6f19a67a Mon Sep 17 00:00:00 2001
From: Dave <dpmartin@yahoo.com>
Date: Sat, 28 Apr 2018 14:08:11 -0400
Subject: [PATCH] Add contentWindow check

When running tests using jest, this component would throw the error: `TypeError: Cannot read property 'addEventListener' of null`, adding the check fixed the issue.
---
 src/Gallery.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Gallery.js b/src/Gallery.js
index 638f2cd..ab8c494 100644
--- a/src/Gallery.js
+++ b/src/Gallery.js
@@ -261,7 +261,7 @@ class Gallery extends Component {
         };
         return (
                 <div id={this.props.id} className="ReactGridGallery" ref={(c) => this._gallery = c}>
-                    <iframe style={resizeIframeStyles} ref={(c) => c && c.contentWindow.addEventListener('resize', this.onResize) } />
+                    <iframe style={resizeIframeStyles} ref={(c) => c && c.contentWindow && c.contentWindow.addEventListener('resize', this.onResize) } />
                 {images}
                 <Lightbox
             images={this.props.images}