Errors in Sesson settings when viewed with Sesson admin theme

When I set  Sasson or its sub-theme as administrative theme and go to it's specific (non-global) settings then I get these notifications:

Notice: Undefined index: theme_settings in sasson_form_system_theme_settings_alter() (line 426 of /var/www/mysite/htdocs/sites/all/themes/sasson/theme-settings.php).
Notice: Undefined index: logo in sasson_form_system_theme_settings_alter() (line 427 of /var/www/mysite/htdocs/sites/all/themes/sasson/theme-settings.php).
Notice: Undefined index: favicon in sasson_form_system_theme_settings_alter() (line 428 of /var/www/mysite/htdocs/sites/all/themes/sasson/theme-settings.php).

It will show its settings, but in the general tab will only appear the Breadcrumb and RSS settings. The Toggle Display, Logo image settings and Shortcut icon settings are missing.

This error only occurs when you look with sasson admin theme in sasson settings. The obvious work around is then to change the administrative theme to one of Drupal's core themes, but that is not always desirable.