Prevent class signup when cancelled

webclient/src/Classes.js

@@ -219,15 +219,19 @@ export function ClassDetail(props) {
 										</div>
 									}
 								</div>
+							:
+								(clazz.is_cancelled ?
+									<p>The class is cancelled.</p>
 								:
 									((clazz.max_students && clazz.student_count >= clazz.max_students) ?
-									<p>The course is full.</p>
+										<p>The class is full.</p>
 									:
 										<Button onClick={handleSignup}>
 											Sign me up!
 										</Button>
 									)
 								)
+							)
 						}
 					</div>
 				: