gives a null pointer at some point

validationError.java

package com.tactico.tm.bugs;

import org.deeplearning4j.nn.api.OptimizationAlgorithm;
import org.deeplearning4j.nn.conf.BackpropType;
import org.deeplearning4j.nn.conf.ComputationGraphConfiguration;
import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
import org.deeplearning4j.nn.conf.Updater;
import org.deeplearning4j.nn.conf.inputs.InputType;
import org.deeplearning4j.nn.conf.layers.RnnOutputLayer;
import org.deeplearning4j.nn.weights.WeightInit;
import org.nd4j.linalg.activations.Activation;
import org.nd4j.linalg.lossfunctions.LossFunctions;

public class ValidationError {
	public static void main (String[] args){
		ComputationGraphConfiguration.GraphBuilder confBuilder = new NeuralNetConfiguration.Builder()
                .iterations(1)
                .optimizationAlgo(OptimizationAlgorithm.STOCHASTIC_GRADIENT_DESCENT)
                .learningRate(0.1)
                .updater(Updater.ADAGRAD)
                .weightInit(WeightInit.XAVIER)
                .regularization(true).useDropConnect(true)
                .dropOut(0.5)
                .graphBuilder()
                .setInputTypes(InputType.recurrent(1))
                .addInputs("input1");
		
		confBuilder.addLayer("output", new RnnOutputLayer.Builder(LossFunctions.LossFunction.MSE)
		        .nIn(1)
		        .nOut(1)
		        .activation(Activation.SIGMOID)
		        .build(), "input1");
		
		confBuilder.setOutputs("output");
		ComputationGraphConfiguration cgconf = confBuilder.pretrain(false)
				.backprop(true).backpropType(BackpropType.Standard)
				.build();
	}

}