orEmpty

Returns this sequence if it's not null and the empty sequence otherwise.

inline fun <T> Sequence<T>?.orEmpty(): Sequence<T>(source)

val nonNullSeq: Sequence<String>? = listOf("a", "b", "c").asSequence()
val nullSeq: Sequence<String>? = null

println("Non‑null sequence:")
nonNullSeq.orEmpty().forEach { println(it) }

println("Null sequence:")
nullSeq.orEmpty().forEach { println(it) }  // nothing printed

Source