Failing test - getId() return string rather than integer

Hi,

I found an issue in a specific case, when you find a child entity (JOINED) which is linked to another child entity.

If I clone the linked child entity and call getId(), it gives the value as 'string' rather than 'integer'. If I set the property id as public, there is no problem.

If I call getId on the child entity rather than the clone, it gives 'integer' as expected. So it's weird...

This simple test demonstrates the problem.
Can you align the test id to the assigned issue ID?