Help with List of Objects Map

Help I just don’t understand what is happening I am getting this error, Uncaught TypeError: Cannot read property ‘map’ of undefined, if I console.log(this.data.probandera) I get an array of objects, {_id: “sdsafsad”, Cuando : “asdafsada”} with that format… but I just dont know how to iterate in them, followed the manual but I always land in the same error… HELP?

C.Testing = React.createClass({

mixins:[ReactMeteorData],

getMeteorData(){

var dato = {}
let carajo = Meteor.subscribe("probando");
if (carajo.ready()){
   dato.probandera = L.Probando.find({}).fetch();
}
return dato;

},

Sub(e){
e.preventDefault();

var nombre = e.target.nombre;
L.Probando.insert({Cuanto : nombre.value}, (err,sub)=>{
      if (err){
        console.log(err);
      } else {
        console.log(sub);
        nombre.value = "";
      }
    }
);

},

renderTasks(){
return this.data.probandera.map((proban)=>{
/* THE UPPER LINE GIVES ME ERROR */
});
},

render: function() {
return (


<form onSubmit={ this.Sub }>

Click me
    <ul>
      { this.renderTasks() }
    </ul>
  </div>
);

}

});