Can not find data record in database table scheduler_slots.

More information about this error
 
 
in the teacher view, when clicking the "Delete selected slots" button without selecting a slot first, Scheduler reacts with the following error message.
 
Debug info: SELECT * FROM {scheduler_slots} WHERE id = ? AND schedulerid = ?
[array (
0 => '',
1 => '1',
)]
Error code: invalidrecord
 
Stack trace:

• line 1533 of /lib/dml/moodle_database.php: dml_missing_record_exception thrown
• line 1509 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()
• line 508 of /mod/scheduler/model/scheduler_instance.php: call to moodle_database->get_record()
• line 197 of /mod/scheduler/teacherview.controller.php: call to scheduler_instance->get_slot()
• line 110 of /mod/scheduler/teacherview.php: call to include()
• line 66 of /mod/scheduler/view.php: call to include()