fix(ssr): avoid missing files in manifest (#11609)

Co-authored-by: chenyj <2932802684@qq.com>
Co-authored-by: johnleider <john@vuetifyjs.com>

Author: 3 people

Diff for: src/server/template-renderer/create-async-file-mapper.js

@@ -44,7 +44,11 @@ function mapIdToFile (id, clientManifest) {
     fileIndices.forEach(index => {
       const file = clientManifest.all[index]
       // only include async files or non-js, non-css assets
-      if (clientManifest.async.indexOf(file) > -1 || !(/\.(js|css)($|\?)/.test(file))) {
+      if (
+        file &&
+        (clientManifest.async.indexOf(file) > -1 ||
+          !/\.(js|css)($|\?)/.test(file))
+      ) {
         files.push(file)
       }
     })