add result unknown for handle

src/core/hle/service/nvnflinger/hos_binder_driver.cpp

@@ -53,6 +53,9 @@ Result IHOSBinderDriver::GetNativeHandle(s32 binder_id, u32 type_id,
     const auto binder = m_server->TryGetBinder(binder_id);
     R_UNLESS(binder != nullptr, ResultUnknown);
 
+    auto native_handle = binder->GetNativeHandle(type_id);
+    R_UNLESS(native_handle != nullptr, ResultUnknown);
+
     *out_handle = binder->GetNativeHandle(type_id);
 
     R_SUCCEED();