Fatal error: Call to a member function format() on a non-object in agres_rconflict.module

Greetings,

When i try to book any nodes of 'categories' type, then i see this error.

Fatal error: Call to a member function format() on a non-object in /var/www/server/data/www/domain.com/sites/all/modules/agreservations/agres_rconflict/agres_rconflict.module on line 223

How to fix?

Thanks.