[BUGFIX] Remove the return type hint for getDepartment

This commit solves a problem with jobs that do not have a department
set

Classes/Domain/Model/Job.php

@@ -210,9 +210,9 @@ class Job extends AbstractEntity {
 	}
 
 	/**
-	 * @return Department
+	 * @return Department|NULL
 	 */
-	public function getDepartment(): Department {
+	public function getDepartment() {
 		return $this->department;
 	}