Fix KClass.java intrinsic for stack values of type Unit

#KT-17692 Fixed

compiler/testData/codegen/box/callableReference/bound/localUnitFunction.kt

@@ -0,0 +1,9 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+
+fun box(): String {
+    fun foo(): Unit {}
+    assert(Unit.javaClass.equals(foo().javaClass))
+    assert(Unit.javaClass.equals(foo()::class.java))
+    return "OK"
+}