Add language_error_empty to the language files, #6495

interface/web/client/lib/lang/ar_client.lng

interface/web/client/lib/lang/bg_client.lng

interface/web/client/lib/lang/br_client.lng

interface/web/client/lib/lang/ca_client.lng

interface/web/client/lib/lang/cn_client.lng

interface/web/client/lib/lang/cz_client.lng

interface/web/client/lib/lang/de_client.lng

interface/web/client/lib/lang/dk_client.lng

interface/web/client/lib/lang/el_client.lng

interface/web/client/lib/lang/en_client.lng

interface/web/client/lib/lang/es_client.lng

interface/web/client/lib/lang/fi_client.lng

interface/web/client/lib/lang/fr_client.lng

interface/web/client/lib/lang/hr_client.lng

interface/web/client/lib/lang/hu_client.lng

interface/web/client/lib/lang/id_client.lng

interface/web/client/lib/lang/it_client.lng

interface/web/client/lib/lang/ja_client.lng

interface/web/client/lib/lang/nl_client.lng

interface/web/client/lib/lang/pl_client.lng