Campo password vacio

[Delek]

He sustituido el 'data' => null por 'always_empty' => true y me lanza el siguiente error:

Código:

The option "always_empty" does not exist. Known options are: "action", "attr", "auto_initialize", "block_name", "by_reference", "cascade_validation", "compound", "constraints", "csrf_field_name", "csrf_message", "csrf_protection", "csrf_provider", "csrf_token_id", "csrf_token_manager", "data", "data_class", "disabled", "empty_data", "error_bubbling", "error_mapping", "extra_fields_message", "first_name", "first_options", "inherit_data", "intention", "invalid_message", "invalid_message_parameters", "label", "label_attr", "mapped", "max_length", "method", "options", "pattern", "post_max_size_message", "property_path", "read_only", "required", "second_name", "second_options", "translation_domain", "trim", "type", "validation_groups", "virtual"

Leí en la documentación que always_empty era por defecto true, lo que no entiendo es por que me dice que no existe o_O