* Notice: Undefined index: interwiki in the function _interwiki_sample_prefix() (row 213 in the file sites/all/modules/interwiki/interwiki.module).
* Notice: Trying to get property of non-object in the function _interwiki_sample_prefix() (row 214 in th file sites/all/modules/interwiki/interwiki.module).

These errors appear on the admin/config/content/formats/wysiwyg_format page, when I open it to add interwiki filter.