String.toBoolean() should be String?.toBoolean() #KT-14119

libraries/stdlib/jdk7/test/UseCloseableResourceTest.kt

@@ -5,14 +5,12 @@
 
 package kotlin.jdk7.test
 
+import test.platformNull
 import java.io.*
-import java.util.*
 import kotlin.test.*
 
 class UseCloseableResourceTest {
 
-    @Suppress("HasPlatformType", "UNCHECKED_CAST") fun <T> platformNull() = Collections.singletonList(null as T).first()
-
     class Resource(val faultyClose: Boolean = false) : Closeable {
 
         var isClosed = false