ERROR `/assets/js/bundle.js' not found.

[alexmodrono]

I was creating my jekyll website using this theme, and when I was running it using jekyll serve, it gives me the following error:

WARN: Unresolved specs during Gem::Specification.reset:
      ffi (< 2, >= 0.5.0)
WARN: Clearing out unresolved specs.
Please report a bug if this causes problems.
Configuration file: /Users/alex/github/Phantom-Page/_config.yml
       Deprecation: The 'gems' configuration option has been renamed to 'plugins'. Please update your config file accordingly.
            Source: src
       Destination: public
 Incremental build: disabled. Enable with --incremental
      Generating... 
                    done in 0.712 seconds.
 Auto-regeneration: enabled for 'src'
    Server address: http://127.0.0.1:4000/
  Server running... press ctrl-c to stop.
[2018-06-13 22:06:48] ERROR `/assets/js/bundle.js' not found.
[2018-06-13 22:06:52] ERROR `/assets/js/bundle.js' not found.