Restore attempt in 3.5 and 3.9 fail - invalid input syntax for integer: ""

[katcher]

The following error occurred when restoring a course: Our db is postgres 9.6

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 => '844d4b17576b42fb59a34f8403fc0cb7',
1 => 'activequiz_question',
2 => '',
)]
Error code: dmlreadexception
×Stack trace:
line 486 of /lib/dml/moodle_database.php: dml_read_exception thrown
line 329 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()
line 920 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()
line 1624 of /lib/dml/moodle_database.php: call to pgsql_native_moodle_database->get_records_sql()
line 1596 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()
line 1575 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()
line 240 of /backup/util/dbops/restore_dbops.class.php: call to moodle_database->get_record()
line 1737 of /backup/util/dbops/restore_dbops.class.php: call to restore_dbops::get_backup_ids_cached()
line 219 of /backup/util/plan/restore_structure_step.class.php: call to restore_dbops::get_backup_ids_record()
line 211 of /backup/util/plan/restore_structure_step.class.php: call to restore_structure_step->get_mapping()
line 202 of /mod/activequiz/backup/moodle2/restore_activequiz_stepslib.php: call to restore_structure_step->get_mappingid()
line 181 of /mod/activequiz/backup/moodle2/restore_activequiz_stepslib.php: call to restore_activequiz_activity_structure_step->recode_activequiz_questionorder()
line 409 of /backup/util/plan/restore_structure_step.class.php: call to restore_activequiz_activity_structure_step->after_execute()
line 113 of /backup/util/plan/restore_structure_step.class.php: call to restore_structure_step->launch_after_execute_methods()
line 181 of /backup/util/plan/base_task.class.php: call to restore_structure_step->execute()
line 210 of /backup/moodle2/restore_activity_task.class.php: call to base_task->execute()
line 178 of /backup/util/plan/base_plan.class.php: call to restore_activity_task->execute()
line 168 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()
line 384 of /backup/controller/restore_controller.class.php: call to restore_plan->execute()
line 219 of /backup/util/ui/restore_ui.class.php: call to restore_controller->execute_plan()
line 143 of /backup/restore.php: call to restore_ui->execute()