Ticket #43005: #43005.diff

wp-admin/js/updates.js

@@ -2423 +2423 @@
                                 return;
                         }
 
-                        if ( 'undefined' === typeof message.action ) {
-                                return;
-                        }
+            if ( null === message  || 'undefined' === typeof message.action ) {
+                return;
+            }
 
                         switch ( message.action ) {