Fix case where invalid response is returned

[KorvinSzanto]

Breaking change

Proposed change

• Fix return type of _process_request
• Pin json result to dict to avoid issues like "foo" being returned from the API
• Change _process_request to return None if a request fails or a response is invalid.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (which adds functionality to an this integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml

Additional information

• This PR fixes or closes issue:
• This PR is related to issue: relates to Tiwi connect API down #47

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• The code has been formatted using Black (black --fast custom_components)

If user exposed functionality or configuration variables are added/changed: