jekyll 4.0.0 | Error: undefined method `[]' for nil:NilClass

## I want to report a bug:
Yes

### What is the current behavior?
When I do **`bundle exec jekyll algolia`** with the API key, it throws an error **`jekyll 4.0.0 | Error: undefined method `[]' for nil:NilClass`**


### What is your expected behavior?
The command should execute successfully

### Git repository to reproduce the issue:

Here is the codebase, it is still in the works: [https://github.com/piyushpaliwal/ipiyush.git](https://github.com/piyushpaliwal/ipiyush.git)

### Ruby version used:

2.6.3p62

### Jekyll version used:

4.0.0.0

Start by reproducing `bundle exec jekyll algolia` in the linked `ipiyush` repository with Ruby 2.6.3 and Jekyll 4.0.0, using the reported API key configuration. Trace the `undefined method [] for nil:NilClass` failure from the command output. Done means the command executes successfully without that error.

Written by the indexing model from the issue text.