Fix mapping of nullable generic underlying types of inline classes

#KT-32162 Fixed

compiler/testData/codegen/box/inlineClasses/callableReferences/let/stringNGeneric2.kt

@@ -0,0 +1,32 @@
+// WITH_STDLIB
+// WORKS_WHEN_VALUE_CLASS
+// LANGUAGE: +ValueClasses, +GenericInlineClassParameter
+
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class Value<T: String>(val value: T?)
+
+object Foo {
+    fun foo(value: Value<String>) {
+        res = value.value
+    }
+
+    fun bar(value: Value<String>?) {
+        res = value?.value
+    }
+}
+
+var res: String? = "FAIL"
+
+fun box(): String {
+    Value<String>("OK").let(Foo::foo)
+    if (res != "OK") return "FAIL 1: $res"
+    res = "FAIL 2"
+
+    Value<String>("OK").let(Foo::bar)
+    if (res != "OK") return "FAIL 3: $res"
+    res = "FAIL 4"
+
+    null.let(Foo::bar)
+    if (res != null) return "FAIL 3: $res"
+    return "OK"
+}