Ticket #47704: 47704-maintenance-nag.diff

src/wp-admin/includes/update.php

@@ -707 +707 @@
                  * This flag is cleared whenever a successful update occurs using Core_Upgrader.
                  */
                 $comparison = ! empty( $failed['critical'] ) ? '>=' : '>';
-                if ( version_compare( $failed['attempted'], $wp_version, $comparison ) ) {
+                if ( isset( $failed['attempted'] ) && version_compare( $failed['attempted'], $wp_version, $comparison ) ) {
                         $nag = true;
                 }
         }