BatchCreateResponseFormatter crashes on None elements in response

[ZLeventer]

Description

BatchCreateResponseFormatter does not guard against None elements in the batch response list. When the API returns a partial response with None entries (e.g., due to a failed individual record in a batch), iterating over the results raises an AttributeError.

Steps to reproduce

1. Make a batch create request where one or more records fail server-side
2. The response contains None elements in the results array
3. BatchCreateResponseFormatter attempts to access attributes on None, raising AttributeError

Expected behavior

The formatter should skip or gracefully handle None elements rather than crashing.

Proposed fix

PR #70 adds a guard against None elements before processing.