Undefined array key "id" in uswds_base_preprocess_form_element()

Problem/Motivation

When I have a validation error on some form elements, the following warning message is thrown:

Warning: Undefined array key "id" in uswds_base_preprocess_form_element() (line 17 of /app/docroot/themes/contrib/uswds_base/preprocess/element/form_element.preprocess.inc).

It doesn't seem to happen with text inputs, but does on textarea elements. I suspect it is also happening on other element types.

Looking at <uswds_base_preprocess_form_element it seems not all form elements have their id set at: $variables['element']['#attributes']['id']. It does seem that the id is always available at: $variables['element']['#id'] however.

Steps to reproduce

1. Build or use a form with a textarea element.
2. Trigger a server-side error on the textarea element, such as being required.
3. A warning Undefined array key "id" in uswds_base_preprocess_form_element() should be printed in the logs.

Proposed resolution

In uswds_base_preprocess_form_element conditionally check that the $variables['element']['#attributes']['id'] or $variables['element']['#id'] items exist before adding them to $variables['error_id'].

Remaining tasks

1. Confirm bug and agree on solution.
2. Create patch implementing solution.

User interface changes

N/A

API changes

N/A

Data model changes

N/A