Reduce dependency on existence of window

Author: fritz-c

src/react-image-lightbox.js

@@ -172,7 +172,7 @@ class ReactImageLightbox extends Component {
 
     // Attach key and mouse input events
     attachListeners() {
-        if (!this.listenersAttached) {
+        if (!this.listenersAttached && typeof window !== 'undefined') {
             window.addEventListener('resize', this.handleWindowResize);
             window.addEventListener('mouseup', this.handleMouseUp);
             window.addEventListener('touchend', this.handleMouseUp);

src/util.js

@@ -4,7 +4,11 @@
  * @return {?number} ieVersion - IE version as an integer, or undefined if not IE
  */
 export function getIEVersion() {
-    const match = navigator.userAgent.match(/(?:MSIE |Trident\/.*; rv:)(\d+)/);
+    if (typeof window === 'undefined') {
+        return undefined;
+    }
+
+    const match = window.navigator.userAgent.match(/(?:MSIE |Trident\/.*; rv:)(\d+)/);
     return match ? parseInt(match[1], 10) : undefined;
 }