fix(symfony): object typed property schema collection restriction

[c1tru55]

Q	A
Branch?	4.0
Tickets	n/a
License	MIT
Doc PR	n/a

in case of Collection constraint with empty fields key (this is valid value for it):

    /**
     * @var array<string, mixed>
     */
    #[Assert\Collection(fields: [])]
    public array $options = [];

properties field is generated as plain array, which is incorrect (must be always object):

        options:
          type: object
          properties: [] <--------
          additionalProperties: false