message: Fix task migration
diff: @@ -89,6 +89,9 @@ class TaskUnitMigration {
  oldUnitObj.tasks = <ITask[]>(await Promise.all(oldUnitObj.tasks.map(async (task) => {
  if (task instanceof ObjectID) {
  const taskData = await Task.findById(task).exec();
  + if (taskData === null) {
  + return null;
  + }
  const taskDataObj = taskData.toObject();
  return taskDataObj;
  } else {
  