jquery-slick-rails | Integrates Slick carousel , a jQuery plugin | Plugin library

I am trying to create a basic email sign up form which displays a bootstrap modal after the email is successfully saved. To keep it simple, I am not doing this via AJAX (i.e. I am reloading the page). The issue is that after successfully redirecting, I am getting the following error in the console:

I am trying to migrate from Rails 4.2 to Rails 5.0 (running on ruby 2.3) (see plan here https://stackoverflow.com/a/38443616/7374136)

The plan is to:

1. Update the rails gem and all dependencies.
2. Run tests (covering almost our whole code base) for depreciations and fix them.
3. Run rake rails:update to update Rails
4. Adapt the configuration, application classes, breaking changes, ...

Nevertheless, I am blocked at the first step already, updating the rails gem and dependencies. gem 'rails', '4.2.5' -> gem 'rails', '~> 5.0' running: bundle update rails.

I faced multiple dependencies issues, which I fixed by looking for any dependencies that ultimately require rails to be less than 5, and see if those can be updated. Running: