do not render anchors to nowhere

src/renderer.ts

@@ -30,16 +30,14 @@ export function create_renderer(opts: MarkdownOptions) {
 function heading(renderer: marked.Renderer, opts: MarkdownOptions) {
 	return function(orig_text: string, level: 1 | 2 | 3 | 4 | 5 | 6, raw: string) {
 		let { text, id, html_attrs } = parse_attributes(raw);
+		if (id) {
+			text += `\n<a class="heading-anchor" href="#${id}">`
+				+ `\n\t\t${icons.link}`
+				+ `\n\t\t<span style="display: none">Section titled ${text}</span>`
+				+ `\n\t</a>`;
+		}
 		
-		return `
+		return `\n<h${level} ${html_attrs.join(' ')}>\n\t${text}\n</h${level}>`;
-<h${level} ${html_attrs.join(' ')}>
-	${text}
-	<a class="heading-anchor" href="#${id}">
-		${icons.link}
-		<span style="display: none">Section titled ${text}</span>
-	</a>
-</h${level}>
-`;
 	};
 }