filterNotNull for Map values

[henrik242]

@pniederw1

@Suppress("UNCHECKED_CAST")
val map3: Map<Int, String> = map2.filterValues { it != null }

I figured out a sane way to do this without a cast:

val map3: Map<Int, String> = map2
    .mapNotNull { it.value?.let { value -> it.key to value} }
    .toMap()