Problem/Motivation
The following PHP error is presented every time the add field form is visited:
Deprecated function: strlen(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\field_ui\Form\FieldStorageAddForm->buildForm() (line 195 of /core/modules/field_ui/src/Form/FieldStorageAddForm.php)
Since PHP 8.1, the function strlen() doesn't allow a null parameter.
Steps to reproduce
Visit the add field form for any content type, for example a Basic page: /admin/structure/types/manage/basic_page/fields/add-field
You will see the PHP error if you have enabled error debugging. Otherwise you can see it in Recent log messages page: /admin/reports/dblog
Proposed resolution
Check if the variable is null before using the strlen() function. Attached a patch.
Remaining tasks
N/A
User interface changes
N/A
API changes
N/A
Data model changes
N/A
Release notes snippet
N/A