Constraint data gets clearead when loading

[arcady-zherdev]

Reported here: https://forum.bryntum.com/viewtopic.php?t=25573

Steps to reproduce:

1. edit Gantt/examples/_datasets/launch-saas.json file - replace tasks with this data:

  "tasks" : {
    "rows" : [{
      "cls": "",
      "name": "A test task",
      "effort": 24,
      "endDate": "2022-05-06T00:00:00+02:00",
      "calendar": null,
      "duration": 3,
      "inactive": null,
      "parentId": null,
      "segments": null,
      "baselines": [],
      "direction": null,
      "startDate": "2022-05-03T00:00:00+02:00",
      "effortUnit": "hour",
      "parentIndex": 4,
      "percentDone": 0,
      "unscheduled": false,
      "durationUnit": "day",
      "effortDriven": false,
      "constraintDate": "2022-05-03T00:00:00+02:00",
      "constraintType": "startnoearlierthan",
      "schedulingMode": "Normal",
      "manuallyScheduled": false,
      "ignoreResourceCalendar": null,
      "id": 28
    }
  ]
  },

3. open advanced demo in a browser

Result: both constraint type and date fields are emply.

[arcady-zherdev]

After checking it looks the writeDirection code cannot handle direction : null properly. So a quick workaround is:

class Task extends TaskModel {

    static $name = 'Task';

    writeDirection(me, transaction, quark, direction, fromWriteConstraintType = false) {
        if (direction) {
            super.writeDirection(...arguments);
        }
        else {
            me.constructor.prototype.write.call(this, me, transaction, quark, direction);
        }
    }

}