#1275 Cannot add another Locale

[Michael Beck]

As reported by Irmtfan:
http://xoops.org/modules/newbb/viewtopic.php?topic_id=76095

No Locale can be added in addition to en_US.
for example i build this locale: Locale fr-FR (French)
I change locale in admin> system> general setting and then I received this error:
Fatal error: Cannot redeclare class XoopsLocale in \xoops26\htdocs\locale\fr_FR\locale.php on line 24