Uncaught PHP Exception: Column 'promote' cannot be null

Problem/Motivation

Saving a node with no value for sticky/promotion leads to a fatal error.

[29-Apr-2016 20:28:15 Europe/Kiev] Uncaught PHP Exception Drupal\Core\Entity\EntityStorageException: "SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'promote' cannot be null: INSERT INTO {node_field_data} (nid, vid, type, langcode, title, uid, status, created, changed, promote, sticky, revision_translation_affected, default_langcode) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9, :db_insert_placeholder_10, :db_insert_placeholder_11, :db_insert_placeholder_12); Array
(
[:db_insert_placeholder_0] => 91
[:db_insert_placeholder_1] => 91
[:db_insert_placeholder_2] => article
[:db_insert_placeholder_3] => ru
[:db_insert_placeholder_4] => [ОТМЕНЕНО] Фестиваль Рок посиделки «Бабье лето» 2016
[:db_insert_placeholder_5] => 69
[:db_insert_placeholder_6] => 1
[:db_insert_placeholder_7] => 1450940817
[:db_insert_placeholder_8] => 1461950895
[:db_insert_placeholder_9] =>
[:db_insert_placeholder_10] => 0
[:db_insert_placeholder_11] => 1
[:db_insert_placeholder_12] => 1
)
" at /.../core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php line 756

This only happens if the stick/promoted form display is set to radios widget.

Proposed resolution

A couple of options spring to mind:

- Add extra validation to make sure that there's always a value for those checkboxes (or other basefields, I think this will happen for all boolean base fields)
- Make sure boolean base fields have to be required when they use the radios widget.
- Disable radios widget for boolean base fields.
- Another option?

Remaining tasks

1. Write a test to prove that this fails
2. Decide a direction for the fix.
3. Implement the fix

User interface changes

Depends on the implementation.

API changes

None

Data model changes

None