You can use the elvis operator and evaluate another block of code with run { ... }:

data?.let {
    // execute this block if not null
} ?: run {
    // execute this block if null
}

But this seems not to be quite as readable as a simple if–else statement.

Also, you might find this Q&A useful:

• In Kotlin, what is the idiomatic way to deal with nullable values, referencing or converting them