title: Null value in column "name" violates not-null constraint when adding new item in django admin
body: <p>I have added a new model to my admin. This is my models.py:</p>
  
  <pre><code>class EngineeringToolAttributeType(models.Model):
      name = models.CharField(max_length=50)
      description = models.CharField(max_length=255, blank=True, null=True)
      api_url = models.CharField(max_length=255, blank=True, null=True)
      api_field = models.CharField(max_length=50, blank=True, null=True)
      active = models.BooleanField(default=True)
  
      def __str__(self):
          return self.name
  </code></pre>
  
  <p>And the admin.py:</p>
  
  <pre><code>from extras.models import EngineeringToolAttributeType
  from django.contrib import admin
  
  class EngineeringToolAttributeTypeAdmin(admin.ModelAdmin):
      fields = ['name', 'description', 'api_url', 'api_field', 'active']
      list_display = ('name', 'description', 'api_url', 'api_field', 'active')
  
  admin.site.register(EngineeringToolAttributeType, EngineeringToolAttributeTypeAdmin)
  </code></pre>
  
  <p>When I try to add (click on add button via the admin), I get this error:</p>
  
  <pre><code>Internal Server Error: /website/admin/extras/engineeringtoolattributetype/add/
  
  IntegrityError at /admin/extras/engineeringtoolattributetype/add/
  null value in column "name" violates not-null constraint
  </code></pre>
  
  <p>This has never happened before. I know name is not allowed to be <code>Null</code>, but I'm still adding a record. How is that possible?</p>