How to add the default value of BeginSignInResult in mutableState?

I am performing two operations in my app. One is to read a list of products and one is authenticate the user and for that I'm using Jetpack Compose. In the ViewModel I have two state objects:

var productListResponse by mutableStateOf<Response<List<Product>>>(emptyList())

That works fine, as I put the default value an empty list. However, the second state object is:

var authInResponse by mutableStateOf<Response<BeginSignInResult>>(???)

That expects a result of type BeginSignInResult. How to add the default value in this case? As null doesn't work.