Ticket #27360: 27360.patch

src/wp-admin/js/theme.js

@@ -47 +47 @@
                 this.set({
                         installURI: install,
                         previewURI: preview,
-                        id: this.get( 'slug' )
+                        id: this.get( 'slug' ) || this.get( 'id' )
                 });
         }
 });