Ticket #25963: 25963.2.diff

src/wp-admin/js/theme.js

@@ -497 +497 @@
                 });
 
                 this.overlay.render();
-                this.$el.append( this.overlay.el );
+                if ( 0 === $( 'div.theme-overlay' ).length ) {
+                        this.$el.append( this.overlay.el );
+                } else {
+                        $( 'div.theme-overlay' ).html( this.overlay.el );
+                }
 
                 this.overlay.screenshotGallery();
 
@@ -646 +650 @@
                 this.routes();
 
                 // Set ups history with pushState and our root
-                Backbone.history.start({ root: themes.data.settings.root });
+                if ( window.history && window.history.pushState ) {
+                        Backbone.history.start({ root: themes.data.settings.root });
+                }
         },
 
         routes: function() {