SQLSTATE[HY000]: General error: 1366 Incorrect string value: '\xF6ln' for column 'visitors_city' at row 1

Steps to reproduce:
1) Set visitor ip 78.34.12.20.
2) Open http://domain.tld

Displayed PDOException: in visitors_exit() (line 192 of /home/git/visitors/visitors.exit.inc).

After set db_insert('visitors') to try catch displayed SQLSTATE[HY000]: General error: 1366 Incorrect string value: '\xF6ln' for column 'visitors_city' at row 1.

Problems with the input of diacritical characters.

GeoIP data for ip 78.34.12.20:

Array
(
[continent_code] => EU
[country_code] => DE
[country_code3] => DEU
[country_name] => Germany
[region] => 07
[city] => K�ln
[postal_code] =>
[latitude] => 50.933300018311
[longitude] => 6.9499998092651
[dma_code] => 0
[area_code] => 0
)

City field have diacritical character.