Add Sequence.orEmpty #KT-16552 Fixed

libraries/stdlib/src/kotlin/collections/Sequences.kt

@@ -47,6 +47,14 @@ private object EmptySequence : Sequence<Nothing>, DropTakeSequence<Nothing> {
     override fun take(n: Int) = EmptySequence
 }
 
+/**
+ * Returns this sequence if it's not `null` and the empty sequence otherwise.
+ * @sample samples.collections.Sequences.Usage.sequenceOrEmpty
+ */
+@SinceKotlin("1.3")
+@kotlin.internal.InlineOnly
+public inline fun <T> Sequence<T>?.orEmpty(): Sequence<T> = this ?: emptySequence()
+
 /**
  * Returns a sequence of all elements from all sequences in this sequence.
  *