Inputs should not display helper text if helperText is set to false without validation errors

[antoinefricker]

What you were expecting:
Setting helperText={false} should hide helperText element in input components.

What happened instead:
An empty paragraph is generated introducing a small vertical offset - 3px by default 😱.

Most of the input components share the same behaviour, but usually RA uses false to prevent a ReactNode parameter to be displayed. Am I wrong on this point?

Steps to reproduce:

• Open simple example below
• Edit any post
• Inspect inputs, helperText elements are outlined for easier tracking

Related code:
https://stackblitz.com/edit/github-hnmzx9?file=src%2Fposts%2FPostEdit.tsx

For example <BooleanInput> generates the following HTML

<div class="MuiFormGroup-root ra-input ra-input-commentable css-dmmspl-MuiFormGroup-root">
  {...}
  <p class="MuiFormHelperText-root css-1d1r5q-MuiFormHelperText-root"></p>
</div>

[fzaninotto]

Fixed by #9037