Added download option for assignment cards

Export PDF Download to hook
Prevented some NaN's

src/dashboards/Teacher.tsx

@@ -226,7 +226,7 @@ export default function TeacherDashboard({user}: Props) {
 					<h2 className="text-2xl font-semibold">Past Assignments ({assignments.filter(pastFilter).length})</h2>
 					<div className="flex flex-wrap gap-2">
 						{assignments.filter(pastFilter).map((a) => (
-							<AssignmentCard {...a} onClick={() => setSelectedAssignment(a)} key={a.id} />
+							<AssignmentCard {...a} onClick={() => setSelectedAssignment(a)} key={a.id} allowDownload/>
 						))}
 					</div>
 				</section>