Getting all webhooks fails if any webhook is in "Error" state

[kardoaw]

Problem description
Trying to use IWebhooksClient.GetAll() while there is a webhook in "Error" state throws the following exception:

Newtonsoft.Json.JsonReaderException: Could not convert string to integer: Error. Path 'data[0].last_http_status', ...

Webhook's LastHttpStatus is not always an integer value, as described here: https://pipedrive.readme.io/docs/guide-for-webhooks#section-status-codes-for-webhooks.

Steps to reproduce

1. Create an endpoint for your new webhook which takes more than ten seconds to execute.
2. Register a new webhook in Pipedrive using your webhook address.
3. Trigger a request to your webhook and wait for the response.
4. Inspect that the webhook is now in "Error" state ("last_http_status":"Error").
5. Try to use webhooks client's GetAll() to get all the webhooks.

Expected behavior
All webhooks are returned.