Error when configuring production AvaTax mode and credentials at website scope

[rsisco]

An error is encountered when attempting to configure the AvaTax extension's mode and credentials at the website scope.

Preconditions

1. Magento 2.2.x
2. AvaTax extension 1.x

Steps to reproduce

1. In Magento backend, navigate to STORES > Settings > Configuration > SALES > Tax > AvaTax Settings
2. Ensure scope is set to default and set Enable AvaTax = No
   
3. Save Configuration
4. Change scope to a specific website
   
5. Enable AvaTax, set Mode = Production, and provide production credentials (account number, license key, and company code)
6. Click 'Save Configuration'

Expected result

1. Magento should report a successful connection to AvaTax with the following message: "Successfully connected to AvaTax using the Production credentials"

Actual result

1. Magento reports one or more configuration values are missing with the following message: "The AvaTax extension is set to "Production" mode, but production credentials are incomplete."

[rsisco]

It looks like the reported error is caused by the method retrieving the production company code not including a scope type. However, once this is fixed, a different error is produced:
"Notice: Undefined index: Production" or "Notice: Undefined index: Development", depending on which mode is chosen.

I've identified some other methods that don't provide a scope type when retrieving config values; and after updating each of those, the problem appears to be fixed.

[rsisco]

This issue has been addressed in release 1.4.5.