api-pagination gem configuration error in Rails 5 when deployed to heroku - heroku

Question

I am using the api-pagination gem and deploying to heroku in a rails 5 app. My configuration is ok in development but fails in production. Here is the config file:
config/initializers/api_pagination.rb
ApiPagination.configure do |config|
# If you have both gems included, you can choose a paginator.
config.paginator = :will_paginate
# By default, this is set to 'Total'
config.total_header = 'X-Total'
# By default, this is set to 'Per-Page'
#config.per_page_header = 'X-Per-Page'
# Optional: set this to add a header with the current page number.
#config.page_header = 'X-Page'
# Optional: what parameter should be used to set the page option
config.page_param = :page
# or
config.page_param do |params|
params[:page][:number]
end
# Optional: what parameter should be used to set the per page option
config.per_page_param = :per_page
# or
config.per_page_param do |params|
params[:page][:size]
end
end
Here is the error from the heroku logs:
[INFO ] Completed 500 Internal Server Error in 1ms (ActiveRecord: 0.0ms)
[FATAL] NoMethodError (undefined method `[]' for nil:NilClass):
[FATAL] config/initializers/api_pagination.rb:18:in `block (2 levels) in <top (required)>'
The controller action is very simple right now:
def index
listings = Listing.where(active: true)
paginate json: listings
end
I am including no parameters in the route.

Answer 1

In my situation, most of the configuration was unnecessary. I'm not sure why it was causing an error but the defaults for my case are fine, except that I use will_paginate. This is my config file and it works:
ApiPagination.configure do |config|
# If you have both gems included, you can choose a paginator.
config.paginator = :will_paginate
end
If someone follows up with a solution that addresses the error, I will accept it. It might be useful for someone else that requires more of the non-default settings.