Undefined offset errors

When depth of heirarchy is 2 levels deep
Notice: Undefined offset: 2 in _hierarchical_select_hierarchy_generate() (line 1865 of /Users/brian/Sites/Aegir/filedepot-7.41/sites/fd.ld/modules/hierarchical_select/hierarchical_select.module).

When depth is 3 or more levels deep
Notice: Undefined offset: 2 in _hierarchical_select_hierarchy_generate() (line 1823 of /Users/brian/Sites/Aegir/filedepot-7.41/sites/fd.ld/modules/hierarchical_select/hierarchical_select.module).

All are ocurrances of the following code block (middle line if the error line):

          $item_type = (count($config['editability']['item_types']) >=  $depth)
            ? t($config['editability']['item_types'][$depth])
            : t('item');