Object item is removed by `flatten()`.

[Kray-G]

Here is the problem.

var a = [{a:1},{b:1}];
System.println(a);
System.println(a.flatten());

The result is as follows.

[{"a":1}, {"b":1}]
{}

Expectation is below.

[{"a":1}, {"b":1}]
[{"a":1}, {"b":1}]