BaseControl: Help text id has undefined value if no id is passed to component

[t-hamano]

Description

As shown in the sample code in the Handbook, the id given to the help text will be undefined if you do not pass an id to the BaseControl component and pass an help text.

Handbook Sample Code

import { BaseControl } from '@wordpress/components';
 
const MyBaseControl = () => (
    <BaseControl help="Pressing the Select an author button will open a modal that allows an advanced mechanism for author selection">
        <BaseControl.VisualLabel>Author</BaseControl.VisualLabel>
        <Button>Select an author</Button>
    </BaseControl>
);

Rendering result

This PR adds a check to see if id is defined when rendering the help text.

Types of changes

Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[Mamaduka]

The solution looks good. Thanks for contributing, @t-hamano.