language is lost when editing a translation group

When you edit (and save) a "translation group" node it loses its language. Then you need to edit it again to set it back.

the problem is that hook_update can't access $node->l10n_group_language as it is stored in "item" type which form element is not passed to hook_update, so the update rewrites the language column with an empty string..

the error message
notice: Undefined property: stdClass::$l10n_group_language in l10n_server\l10n_groups\l10n_groups.module on line 81.

the patch also improves the displayed language.. instead language code the language name is displayed when editing the translation group. hu -> Hungarian..