Null-terminate Collection.toArray destination only in JVM

In other platforms the elements following the collection elements
should not be changed.

As a part of efforts to stabilize Native stdlib.

libraries/stdlib/js/src/kotlin/collectionJs.kt

@@ -54,12 +54,11 @@ internal actual fun <T> copyToArrayImpl(collection: Collection<*>, array: Array<
     while (iterator.hasNext()) {
         array[index++] = iterator.next().unsafeCast<T>()
     }
-    if (index < array.size) {
-        array[index] = null.unsafeCast<T>()
-    }
-    return array
+    return terminateCollectionToArray(collection.size, array)
 }
 
+internal actual fun <T> terminateCollectionToArray(collectionSize: Int, array: Array<T>): Array<T> = array
+
 /**
  * Returns a new read-only list containing only the specified object [element].
  *

libraries/stdlib/js/src/kotlin/collections/ArrayList.kt

@@ -171,11 +171,7 @@ public actual open class ArrayList<E> internal constructor(private var array: Ar
 
         (this.array as Array<T>).copyInto(array)
 
-        if (array.size > size) {
-            array[size] = null as T // null-terminate
-        }
-
-        return array
+        return terminateCollectionToArray(size, array)
     }
 
     override fun toArray(): Array<Any?> {