fixed SQL error

classes/exporters/CourseExporter.php

@@ -367,7 +367,7 @@ class CourseExporter extends Exporter
                 'INNER JOIN `seminar_inst` USING (`seminar_id`)
                 INNER JOIN `semester_courses`
                     ON `seminare`.`seminar_id` = `semester_courses`.`course_id`
-                WHERE `institut_id` = :institute_id,
+                WHERE `seminar_inst`.`institut_id` = :institute_id
                 AND `semester_id` = :semester_id',
                 [
                     'institute_id' => $institute->id,