ReportService::getReportInputControls() error in line 66

[Orajo]

$json_obj = json_decode($data);
[...]
foreach ($json_obj->inputControlState as $state) {
$result[] = \Jaspersoft\Dto\Report\InputControl::createFromJSON($state);
}

In this fragment there is an error, because JSON data are first decoded, and then passed as argument to createFromJSON, which expects JSON data:

public static function createFromJSON($json)
{
$data_array = json_decode($json, true);

and above line triggers error