If you are not planning to modify "persona" in the User Task, then is should be enough to remove it from the Result Mapping attribute of "Solicitud Empleado".
But, if the User Tasks modifies "persona" in any way, you need to pass it in the Map recevied by:
public void completeTask(User user, TaskSummary task, Map data)
I think, that in your case, you need to pass variable 'm' to the completeTask() method. As far as I can see, you are declaring the Map, setting "persona" in it, but then you are not passing it (as the third parameter) to the completeTask() method.