v2.6.1: Enhance TextControl to correctly map nulls to boolean entity properties

Hidden form fields (e.g., checkboxes or selects in toggled-off sections) often submit `null`. Previously, this could lead to `TypeError` or incorrect persistence if a non-nullable boolean entity property received `null`.

This update ensures that:
*   Non-nullable boolean properties receive `false` when `null` is submitted.
*   Nullable boolean properties correctly retain `null` when `null` is submitted.

This provides robust handling for various form control states and prevents unexpected errors.