Admin CP > Contact page Settings.

When pressing submit, whether the text box is added to or not, I get a General Error:
General Error
SQL ERROR [ mysqli ]

Duplicate entry 'contact_admin_info_flags' for key 'PRIMARY' [1062]

SQL

INSERT INTO phpbb_config_text (config_name, config_value) VALUES ('contact_admin_info_flags', '7')

BACKTRACE

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

FILE: [ROOT]/phpbb/db/driver/driver.php
LINE: 844
CALL: trigger_error()

FILE: [ROOT]/phpbb/db/driver/mysqli.php
LINE: 194
CALL: phpbb\db\driver\driver->sql_error()

FILE: [ROOT]/phpbb/db/driver/factory.php
LINE: 329
CALL: phpbb\db\driver\mysqli->sql_query()

FILE: [ROOT]/phpbb/config/db_text.php
LINE: 111
CALL: phpbb\db\driver\factory->sql_query()

FILE: [ROOT]/includes/acp/acp_contact.php
LINE: 93
CALL: phpbb\config\db_text->set_array()

FILE: [ROOT]/includes/functions_module.php
LINE: 666
CALL: acp_contact->main()

FILE: [ROOT]/adm/index.php
LINE: 81
CALL: p_master->load_active()