fix: [scripts] Add null check in highlight wrapper

This change enables re-using highlight wrapper for components without
the toolbar and copy buttons e.g. slides.

Remove commented code in copy to clipboard.

Author: manid2

assets/scripts/copy.js

@@ -2,8 +2,14 @@ const hiTextBlock = document.querySelectorAll(".highlight-wrapper");
 
 hiTextBlock.forEach(function (hiTextBlock) {
   const hiToolbar = hiTextBlock.querySelector(".highlight-toolbar");
+  if (!hiToolbar) return;
+
   const hiText = hiTextBlock.querySelector(".highlight");
+  if (!hiText) return;
+
   const copyButton = hiToolbar.querySelector(".js-btn-copy-code");
+  if (!copyButton) return;
+
   copyButton.classList.remove("hide");
 
   /* Borrowed from adityatelange/hugo-PaperMod theme. */
@@ -16,15 +22,6 @@ hiTextBlock.forEach(function (hiTextBlock) {
 
   /* copy code in pre > code blocks */
   copyButton.addEventListener("click", () => {
-    /* Disabled to keep line numbers inline.
-    // Use clipboard API if available.
-    if ("clipboard" in navigator) {
-      navigator.clipboard.writeText(hiText.innerText);
-      copyingDone();
-      return;
-    }
-    */
-
     // Fallback to selection and copy
     const range = document.createRange();
     range.selectNodeContents(hiText);