feat: add fallback state for empty table of contents

apps/website/app/[locale]/blog/[slug]/components/TableOfContents.tsx

@@ -47,6 +47,8 @@ export function TableOfContents() {
 		<nav className="space-y-2 text-sm">
 			<p className="font-medium mb-4">Table of Contents</p>
 			<ul className="space-y-2">
+				{headings.length > 0 ? (
+					<>
 						{headings.map((heading) => (
 							<li
 								key={heading.id}
@@ -70,6 +72,12 @@ export function TableOfContents() {
 								</a>
 							</li>
 						))}
+					</>
+				) : (
+					<li>
+						<p className="text-muted-foreground">No headings found</p>
+					</li>
+				)}
 			</ul>
 		</nav>
 	);