Fix NoMethodError in JobWebhook when error is nil

[HarisDelalic]

Summary

Fix NoMethodError in JobWebhook#initialize when the error key is present but value is nil.

Problem

When the API returns a response like:

{"id": "12345678-1234-1234-1234-123456789012", "status": "Processing", "error": null}

The JobWebhook initializer would call ErrorResponse.new(nil), causing:
NoMethodError: undefined method '[]' for nil

Solution

Updated JobWebhook#initialize to match the existing pattern in Job#initialize:
unless server_response['error'].nil? || server_response['error'].empty?
  @error = ErrorResponse.new(server_response['error'])
end

Test plan

- Added unit tests for JobWebhook covering all edge cases

<img width="1460" height="352" alt="PR_description_img" src="https://github.com/user-attachments/assets/64591692-8d35-4d88-9b43-ef0596d717de" />

[sebastianMindee]

First off, thank you very much for taking the time to do this. The vast majority of people don't care enough to help, so this is like a breath of fresh air.

Secondly, there is a couple of issue with the PR I'd like you to fix if possible:

• The error checks don't need to account for {}. Both in the test and the constructor.
• The error type is correct in the docstring but invalid in steep (my bad), can you update it? should be attr_reader error: ErrorResponse? instead of attr_reader error: ErrorResponse in sig/mindee/parsing/v2/job_webhook.rbs .
• The linting checks are failing for me. Please run bundle exec rubocop -A before committing.

Once done, I can release later today or tomorrow at the latest if all goes well.

Thank you!

[sebastianMindee]

Should never happen. And I think it would be important for this to break if an unexpected error was loaded.

[sebastianMindee]

Suggested change

	unless server_response['error'].nil? || server_response['error'].empty?
	@error = ErrorResponse.new(server_response['error'])
	end
	unless server_response['error'].nil?
	@error = ErrorResponse.new(server_response['error'])
	end

Empty error shouldn't be possible. Only valid objects or null.

[sebastianMindee]

Amazing thanks 🙏