Error: Call to a member function getPendingTransaction() on null [Symfony2]

Question

I'm developing a e-commerce website. I want to allow users to make the payment with Paypal.So i installed and configured the following bundle:

"jms/security-extra-bundle": "dev-master",
"jms/payment-core-bundle": "master-dev",
"jms/di-extra-bundle": "1.7.0",
"jms/payment-paypal-bundle": "dev-master"

I have the following error when i click on the button Pay:

Error: Call to a member function getPendingTransaction() on null

$instruction = $commande->getPaymentInstruction();
        if (null === $pendingTransaction = $instruction->getPendingTransaction()) {
            $payment = $this->ppc->createPayment($instruction->getId(), $instruction->getAmount() - $instruction->getDepositedAmount());
        } else {
            $payment = $pendingTransaction->getPayment();

This is my controllers:

    /**
     * @Route("/complete/{id}", name = "payment_complete")
     */
    public function completeAction(Commandes $commande) // id of the order
    {

        $instruction = $commande->getPaymentInstruction();
        if (null === $pendingTransaction = $instruction->getPendingTransaction()) {
            $payment = $this->ppc->createPayment($instruction->getId(), $instruction->getAmount() - $instruction->getDepositedAmount());
        } else {
            $payment = $pendingTransaction->getPayment();
        }

        $result = $this->ppc->approveAndDeposit($payment->getId(), $payment->getTargetAmount());
        if (Result::STATUS_PENDING === $result->getStatus()) {
            $ex = $result->getPluginException();

            if ($ex instanceof ActionRequiredException) {
                $action = $ex->getAction();

                if ($action instanceof VisitUrl) {
                    return new RedirectResponse($action->getUrl());
                }

                throw $ex;
            }
        } else if (Result::STATUS_SUCCESS !== $result->getStatus()) {
            throw new \RuntimeException('Transaction was not successful: ' . $result->getReasonCode());
        }
        // if successfull, i render my order validation template
        return $this->render('FLYBookingsBundle:Post:validation.html.twig', array('commande' => $commande));

    }

    /** @DI\LookupMethod("form.factory") */
    protected function getFormFactory()
    {
    }

    /**
     * @Route("/cancel", name = "payment_cancel")
     */
    public function CancelAction()
    {
        $this->get('session')->getFlashBag()->add('info', 'Transaction annulée.');
        return $this->redirect($this->generateUrl('yourTemplate'));
    }

}

This is my entity commandes:

<?php

namespace FLY\BookingsBundle\Entity;
use Application\Sonata\UserBundle\Entity\User;
use Doctrine\ORM\Mapping as ORM;
use JMS\Payment\CoreBundle\Entity\PaymentInstruction;
/**
 * Commandes
 *
 * @ORM\Table("commandes")
 * @ORM\Entity(repositoryClass="FLY\BookingsBundle\Entity\CommandesRepository")
 */
class Commandes
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="Application\Sonata\UserBundle\Entity\User", inversedBy="commandes")
     * @ORM\JoinColumn(nullable=true)
     */
    private $user;

    /**
     * @var boolean
     *
     * @ORM\Column(name="confirm", type="boolean")
     */
    private $confirm;

    /**
     * @var \DateTime
     *
     * @ORM\Column(name="date", type="datetime")
     */
    private $date;

    /**
     * @var integer
     *
     * @ORM\Column(name="reference", type="integer")
     */
    private $reference;

    /**
     * @var array
     *
     * @ORM\Column(name="commande", type="array")
     */
    private $commande;

    /**  * @ORM\OneToOne(targetEntity="JMS\Payment\CoreBundle\Entity\PaymentInstruction")
     */
    private $paymentInstruction;

    public function getPaymentInstruction()
    {
        return $this->paymentInstruction;
    }

    public function setPaymentInstruction(PaymentInstruction $instruction)
    {
        $this->paymentInstruction = $instruction;
    }

    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set confirm
     *
     * @param boolean $confirm
     * @return Commandes
     */
    public function setConfirm($confirm)
    {
        $this->confirm = $confirm;

        return $this;
    }

    /**
     * Get confirm
     *
     * @return boolean 
     */
    public function getConfirm()
    {
        return $this->confirm;
    }

    /**
     * Set date
     *
     * @param \DateTime $date
     * @return Commandes
     */
    public function setDate($date)
    {
        $this->date = $date;

        return $this;
    }

    /**
     * Get date
     *
     * @return \DateTime 
     */
    public function getDate()
    {
        return $this->date;
    }

    /**
     * Set reference
     *
     * @param integer $reference
     * @return Commandes
     */
    public function setReference($reference)
    {
        $this->reference = $reference;

        return $this;
    }

    /**
     * Get reference
     *
     * @return integer 
     */
    public function getReference()
    {
        return $this->reference;
    }

    /**
     * Set commande
     *
     * @param array $order
     * @return Commandes
     */
    public function setCommande($commande)
    {
        $this->commande = $commande;

        return $this;
    }

    /**
     * Get commande
     *
     * @return array 
     */
    public function getCommande()
    {
        return $this->commande;
    }

    /**
     * Set user
     *
     * @param \Application\Sonata\UserBundle\Entity\User $user
     * @return Commandes
     */
    public function setUser(\Application\Sonata\UserBundle\Entity\User $user = null)
    {
        $this->user = $user;
        return $this;

    }

    /**
     * Get user
     *
     * @return \Application\Sonata\UserBundle\Entity\User
     */
    public function getUser()
    {
        return $this->user;
    }
}

Answer 1

Without knowing these components, your

$instruction = $commande->getPaymentInstruction();

returns null and in the next line in the if you calling the function on a null:

$instruction->getPendingTransaction()