When the teacher cancels an appointment with a student, an e-mail is sent to the student.

This e-mail is sent to an incorrect e-mail address - i.e., it does not go to the student(s) associated with the slot, but to an entirely different student.

The reason is an incorrect use of the database fields "id" vs. "studentid" in the "mdl_scheduler_appointment" table, used in teacherview.controller.php. I attach a diff.