When restore a backup with some kind of question we obtain this error:

Debug info: ERROR: invalid input syntax for integer: ""
SELECT * FROM mdl_backup_ids_temp WHERE backupid = $1 AND itemname = $2 AND itemid = $3
[array (
0 => 'c0b9885ca347e1c38ecbee4c71c7a950',
1 => 'question',
2 => '',
)]
Error code: dmlreadexception
Stack trace:
line 423 of /lib/dml/moodle_database.php: dml_read_exception thrown
line 248 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()
line 753 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()
line 1397 of /lib/dml/moodle_database.php: call to pgsql_native_moodle_database->get_records_sql()
line 1369 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()
line 1348 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()
line 223 of /backup/util/dbops/restore_dbops.class.php: call to moodle_database->get_record()
line 1511 of /backup/util/dbops/restore_dbops.class.php: call to restore_dbops::get_backup_ids_cached()
line 213 of /backup/util/plan/restore_structure_step.class.php: call to restore_dbops::get_backup_ids_record()
line 205 of /backup/util/plan/restore_structure_step.class.php: call to restore_structure_step->get_mapping()
line 204 of /backup/moodle2/restore_plugin.class.php: call to restore_structure_step->get_mappingid()
line 107 of /question/type/multianswer/backup/moodle2/restore_qtype_multianswer_plugin.class.php: call to restore_plugin->get_mappingid()
line 84 of /backup/moodle2/restore_plugin.class.php: call to restore_qtype_multianswer_plugin->after_execute_question()
line 362 of /backup/util/plan/restore_structure_step.class.php: call to restore_plugin->launch_after_execute_methods()
line 108 of /backup/util/plan/restore_structure_step.class.php: call to restore_structure_step->launch_after_execute_methods()
line 153 of /backup/util/plan/base_task.class.php: call to restore_structure_step->execute()
line 167 of /backup/util/plan/base_plan.class.php: call to base_task->execute()
line 157 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()
line 315 of /backup/controller/restore_controller.class.php: call to restore_plan->execute()
line 147 of /backup/util/ui/restore_ui.class.php: call to restore_controller->execute_plan()
line 46 of /backup/restore.php: call to restore_ui->execute()