If config.server_bundle_js_file is blank, nil, commented out, and prerendering is done, page request hangs

[justin808]

Here's the default config:

  config.server_bundle_js_file = "server-bundle.js"

There apparently is no check if the server_bundle_js_file is undefined, blank.

A non-blank file name gives an appropriate error.

The current "hanging" behavior is very frustrating.