AssertionError when trying to add a field to an entity bundle

Problem/Motivation

When I try to add a field to any entity type's bundle, I get this error:

AssertionError: "Field" must be defined in MODULE_NAME.field_type_categories.yml in assert() (line 195 of core/lib/Drupal/Core/Field/FieldTypePluginManager.php).

This seems to be caused by Patternkit's custom field named "Serialized field data".

Steps to reproduce

- Configure PHP's assert.active to be enabled, so that failed assert() calls throw exceptions.
- Install Drupal core 10.3 using Standard profile
- Install Patternkit 9.1.0-beta10
- Log in as admin
- Try to add a field to "Basic page" content type.
- Notice that you get the above-listed message (you may see it printed on the page or in the logs).

Proposed resolution

Remove the "Field" category from Patternkit's custom field, because this category does not exist.