Catching an exception on Send. This happens when request for HEAD returns 405 Method Not Allowed. Instead of error http status, this may throw an exception. Return false and fallback to link download.

src/FileSaver.js

@@ -49,7 +49,11 @@ function corsEnabled (url) {
   var xhr = new XMLHttpRequest()
   // use sync to avoid popup blocker
   xhr.open('HEAD', url, false)
-  xhr.send()
+  try {
+    xhr.send();
+  }catch(e) {
+    return false;
+  }
   return xhr.status >= 200 && xhr.status <= 299
 }