Fix popstate event handler in WCF.ImageViewer

diff --git a/wcfsetup/install/files/js/WCF.ImageViewer.js b/wcfsetup/install/files/js/WCF.ImageViewer.js
index d97d3da4c18e47f208bc252accdb1ef2b036d85a..569d909349c2046aa414e3e386f6098faa891b9b 100644 (file)
--- a/wcfsetup/install/files/js/WCF.ImageViewer.js
+++ b/wcfsetup/install/files/js/WCF.ImageViewer.js
@@ -318,7 +318,7 @@ $.widget('ui.wcfImageViewer', {
                this.element.click($.proxy(this.open, this));
 
                window.addEventListener('popstate', (function(event) {
-                       if (event.state.name === 'imageViewer') {
+                       if (event.state != null && event.state.name === 'imageViewer') {
                                if (event.state.container === this._eventNamespace) {
                                        this.open(event);
                                        this.showImage(event.state.image);