Initialize nullable properties to null

[angelolloqui]

In swift, nullable properties have a default value of nil. However, in Kotlin they need explicit initialization.

Example:

This Swift:

class PaymentSelectorPresenter {
    private var selectedPaymentMethod: PaymentMethod?
}

Translates to:

class PaymentSelectorPresenter {
    private var selectedPaymentMethod: PaymentMethod?
}

But should be:

class PaymentSelectorPresenter {
    private var selectedPaymentMethod: PaymentMethod? = null
}

[angelolloqui]

Fixed on 80fcbaa