In ACP - Customise - Language packs - choose any language - Language entries. When I click on "Submit and upload file" button I get following error:

General Error
Method does not exist.

BACKTRACE

FILE: (not given by php)
LINE: (not given by php)
CALL: msg_handler()

FILE: [ROOT]/includes/acp/acp_language.php
LINE: 143
CALL: trigger_error()

FILE: [ROOT]/includes/functions_module.php
LINE: 571
CALL: acp_language->main()

FILE: [ROOT]/adm/index.php
LINE: 71
CALL: p_master->load_active()