This is similar to commit 6bb241cc (ODT
export: fix lost <text:user-field-decl> for fields in tables in headers,
2019-05-29), but here the container we want to ignore (between the
header and the field) is a text frame, not a table cell.
Reviewed-on: https://gerrit.libreoffice.org/73205Reviewed-by: Miklos Vajna <email@example.com>