error nom.1452 to add image to room

hi,

when i tray to add image to room, this error Appears.

1452 Cannot add or update a child row: a foreign key constraint fails (`cometoir_rese`.`rti8l_sr_room_types`, CONSTRAINT `fk_sr_room_types_sr_reservation_assets1` FOREIGN KEY (`reservation_asset_id`) REFERENCES `rti8l_sr_reservation_assets` (`id`) ON DELETE NO AC) SQL=UPDATE `rti8l_sr_room_types` SET `reservation_asset_id`='',`name`='5 person',`alias`='5person-room',`description`='',`state`='1',`checked_out`='890',`checked_out_time`='2015-09-20 10:43:08',`created_by`='0',`created_date`='2015-09-18 11:02:39',`modified_by`='890',`modified_date`='2015-09-20 10:43:30',`language`='*',`params`='{\"show_smoking_option\":\"1\",\"show_child_option\":\"1\"}',`featured`='0',`ordering`='12',`occupancy_adult`='4',`occupancy_child`='2',`smoking`='0' WHERE `id`='28'