don't treat user_id as array, remove duplicate check, fixes #1743

Closes #1743

Merge request studip/studip!1135

app/controllers/course/basicdata.php

@@ -625,8 +625,8 @@ class Course_BasicdataController extends AuthenticatedController
                         $lecturers = $sem->getMembers();
                         foreach ($deputies as $deputy) {
                             // ..but only if not already set as lecturer or deputy.
-                            if (!isset($lecturers[$deputy['user_id']]) && !Deputy::isDeputy($deputy['user_id'], $course_id)) {
-                                Deputy::addDeputy($deputy['user_id'], $course_id);
+                            if (!isset($lecturers[$deputy])) {
+                                Deputy::addDeputy($deputy, $course_id);
                             }
                         }
                     }