fix: add toc slug judge

src/components/blog/TOCHeading.astro

@@ -35,10 +35,12 @@ const {
 			link.addEventListener('click', (event) => {
 				event.preventDefault()
 				const slug = link.getAttribute('data-slug')
+				if (slug) {
 					const element = document.getElementById(slug)
 					if (element) {
 						element.scrollIntoView({ behavior: 'smooth' })
 					}
+				}
 			})
 		})
 	})