Critical error when using Editable Fields with Layout Builder and view mode block

Problem/Motivation

Steps to reproduce

Enable the Editable Fields module.
Configure a view mode for node with editable fields.
Create a block that uses this view mode.
Use Layout Builder and try to add the block to a layout (e.g., for a content type or node).
Observe the error: AssertionError: Cannot load the node entity with NULL ID.

Proposed resolution

The patch adds a defensive check in the EditableFields form builder. It ensures that the entity is valid and has an ID before attempting to load it. This avoids triggering the core assertion when rendering blocks inside Layout Builder (before the entity exists).