Sometimes, this error appears when creating new nodes which contain taxonomy reference fields:

Notice: Undefined index: und in bulk_media_upload_upload_form_submit() (line 112 of /var/www/clients/client2/web59/web/sites/all/modules/bulk_media_upload/bulk_media_upload.upload.inc).
Warning: Invalid argument supplied for foreach() in bulk_media_upload_upload_form_submit() (line 112 of /var/www/clients/client2/web59/web/sites/all/modules/bulk_media_upload/bulk_media_upload.upload.inc).

I tested it with fields that do not autocreate terms.