JVM KT-47365 add box test

compiler/testData/codegen/box/when/kt47365.kt

@@ -0,0 +1,20 @@
+// WITH_RUNTIME
+
+enum class EType {
+    A
+}
+
+class Wrapper(var t: EType?)
+
+fun box(): String {
+    val l = listOf(Wrapper(EType.A), Wrapper(null))
+
+    val ll = l.map {
+        when (it.t) {
+            EType.A -> "O"
+            null -> "K"
+        }
+    }
+
+    return ll[0] + ll[1]
+}