如何过滤在其中一个项目中具有“ null”值的猫鼬模式？

I am fairly new to Coding and JavaScript altogether. I am trying to render the Data inside stored inside my MongoDB in my EJS template. The specific code is here in app.js

// Individual Customer's page
app.get("/customers/all-customers/:customerPhoneNumber", function (req, res) {
  const requestedCustomerPhoneNumber = req.params.customerPhoneNumber;
  Customer.findOne({ phone: requestedCustomerPhoneNumber }, function (
    err,
    foundCustomer
  ) {
    Purchase.find({ customerPhone: requestedCustomerPhoneNumber }, function (
      err,
      foundPurchases
    ) {
      // console.log(foundPurchases);

      foundPurchases.forEach(function (purchase) {
        const planPurchaseID = purchase.purchaseID;
        CompletedSession.findOne({ planPurchaseID: planPurchaseID }, function (err, foundSession) {
          res.render("customer-page", {
            customerPurchases: foundPurchases,
            pageTitle: foundCustomer.name,
            customerID: foundCustomer._id,
            customerPhone: foundCustomer.phone,
            customerWhatsapp: foundCustomer.whatsappNumber,
            customerEmail: foundCustomer.email,
            customerDOB: foundCustomer.dob,
            customerGender: foundCustomer.gender,
            customerRegDate: foundCustomer.registrationDate,
            comletedSessions: foundSession.sessions,
          });
        })
      })
    });
  });
});

In this code, Some of the document has null value of sessions in foundSession, which cause my program to crash when I try to render the array with forEach() loop. Is there any way to automatically drop foundSession with null value of sessions so that I can only pass the foundSession that has no null value of sessions and prevent my program from crashing?