title: Django FieldError at /admin/ in Multidropdown Filter
body: <p>In the django i am geeting this error,</p>
  <p>my models.py</p>
  <pre><code>class User(MasterDataBaseModel):
      user_name = models.CharField(max_length=255,verbose_name=_(&quot;username&quot;))
      gender = models.ForeignKey(Gender, null=True, blank=True, on_delete=models.CASCADE, verbose_name=_(&quot;Gender&quot;))
          
  </code></pre>
  <p>the admin.py</p>
  <pre><code>class Useradmin(DuplicateMixin, MasterDataBaseAdmin):
  form = forms.UserForm
  search_fields = [&quot;user_name&quot;,&quot;Gender&quot;]
  ordering = [&quot;user_name&quot;]
  list_filter = [
      &quot;users_name&quot;,
      (&quot;Gender&quot;,MultiSelectDropdownFilter), ]
  
  list_display = [
      &quot;user_name&quot;,
      &quot;Gender&quot;,]
  </code></pre>
  <p>getting this error ,FieldError at /admin/registration/user/</p>