title: NOT NULL constraint failed for ForeignKey(null=True)
body: <p>I have two models, namely <code>Applicant</code> and <code>LoanRequest</code>. Whenever an <code>Applicant</code> instance is created, a signal is sent to a function that makes an API call. The data from the call, along with the primary key of the instance that sent the signal, is saved to as a <code>LoanRequest</code>. </p>
  
  <p>When I save the <code>LoanRequest</code>, however, it gives the following error:</p>
  
  <pre><code>django.db.utils.IntegrityError: NOT NULL constraint failed: queues_loanrequest.dealer_id_id
  </code></pre>
  
  <p>Here's my code:</p>
  
  <pre><code>class Applicant(models.Model):
      app_id = models.CharField(max_length=100)
      first_name = models.CharField(max_length=100)
      last_name = models.CharField(max_length=100)
      email = models.CharField(max_length=100)
      date_posted = models.DateTimeField(default=timezone.now)
  
      def __str__(self):
          return self.first_name + " " + self.last_name
  
  
  class LoanRequest(models.Model):
      loan_request_id = models.CharField(max_length=100)
      app_id = models.ForeignKey(Applicant, on_delete=models.CASCADE)
      FICO_score = models.CharField(max_length=100)
      income_risk_score = models.CharField(max_length=100)
      DTI = models.CharField(max_length=100)
      date_requested = models.DateTimeField(default=timezone.now)
      loan_request_status = models.CharField(max_length=100,blank=True)
      dealer_id = models.ForeignKey(Dealer, on_delete=models.CASCADE,blank=True)
  
  def credit_check(sender, instance, **kwargs):
      credit_json = get_credit(instance.pk) #credit information for applicant
      credit_json = json.loads(credit_json)
      new_request = LoanRequest.objects.create(app_id=instance, FICO_score=credit_json["ficco-score"],
                                  income_risk_score=credit_json["income-risk-score"],
                                 DTI=credit_json["DTI"])
  
  
  </code></pre>
  
  <p>Very new to Django, would greatly appreciate help!</p>