Do not unbox nullable Result, since before usage it is coerced

#KT-46505

compiler/testData/codegen/box/inlineClasses/unboxGenericParameter/lambda/nullableResult.kt

@@ -0,0 +1,18 @@
+// !LANGUAGE: +InlineClasses
+// WITH_RUNTIME
+
+fun <T> foo(a: Result<T>?): T? = bar(a) {
+    it?.getOrThrow()
+}
+
+fun <T, R> bar(value: T, f: (T) -> R): R {
+    return f(value)
+}
+
+fun box(): String {
+    var res = foo<Int>(Result.success(40))?.plus(2)
+    if (res != 42) return "FAIL $res"
+    res = foo<Int>(null)
+    if (res != null) return "FAIL $res"
+    return "OK"
+}