I saw the following notice when upgrading a site from Moodle 2.3 to integration master as at 16/04/13.

Notice: Undefined property: stdClass::$customtoolbar

1. Time Memory Function Location
   1 0.0013 661624
   Unknown macro: {main}

   ( ) ../upgradesettings.php:0
   2 4.7902 66561120 admin_output_new_settings_by_page( ) ../upgradesettings.php:25
   3 5.0560 69357080 admin_output_new_settings_by_page( ) ../adminlib.php:6579
   4 5.0560 69359480 admin_output_new_settings_by_page( ) ../adminlib.php:6579
   5 5.0926 69381096 admin_output_new_settings_by_page( ) ../adminlib.php:6579
   6 5.2050 70179048 admin_setting_confightmleditor->output_html( ) ../adminlib.php:6604
   7 5.2052 70179936 tinymce_texteditor->use_editor( ) ../adminlib.php:1984
   8 5.2053 70182632 tinymce_texteditor->get_init_params( ) ../lib.php:105

The notice was seen on the upgrade settings page at the end of the upgrade.

Tested upgrading to 2.4 and that was not affected, so master only.