JArray.getRange() has thread-safety problem

```dart
Future getIcon(String packageName) async {
final JArray jArray = await getIconFromAndroid(packageName);

// There is a thread safety issue with the following line of code,
return jArray.getRange(0, jArray.length).buffer.asUint8List();
}
```

**multiple executions test(), the return value maybe incorrect.**
```dart
Isolate.run(() async {
final icon = getIcon('package1'); // maybe incorret
});
Isolate.run(() async {
final icon = getIcon('package2'); // maybe incorret
});
```