fix: add elements to missing dom elements check

src/wwwroot/index.js

@@ -22,7 +22,9 @@ document.addEventListener("DOMContentLoaded", () => {
     !fileInputElement ||
     !chunksDisplayElement ||
     !fileIdElement ||
-    !fileStatusElement
+    !fileStatusElement ||
+    !fileDownloadElement ||
+    !downloadLinkElement
   ) {
     throw new Error("Required DOM elements missing.");
   }