Steps to reproduce

1. Go to AdminUI
2. Choose Admin and then Content Types
3. Create a new Content Type
4. Add Selection field, do not configure any options
5. Try to save Content Type

Current behavior
The 500 error is thrown, with a message:

Warning: reset() expects parameter 1 to be array, null given [in vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/FieldType/Selection/Type.php:90]

Expected behavior
Validation error saying that there is no selection options configured should be displayed.