Disable create post button when community is deleted or removed.

- Fixes #167

ui/src/components/sidebar.tsx

@@ -115,7 +115,7 @@ export class Sidebar extends Component<SidebarProps, SidebarState> {
           <li class="list-inline-item"><Link class="text-info" to={`/u/${mod.user_name}`}>{mod.user_name}</Link></li>
         )}
       </ul>
-      <Link class="btn btn-sm btn-secondary btn-block mb-3" 
+      <Link class={`btn btn-sm btn-secondary btn-block mb-3 ${(community.deleted || community.removed) && 'no-click'}`}
           to={`/create_post/c/${community.name}`}>Create a Post</Link>
       <div>
         {community.subscribed