title: Remove blank "---------" from RadioSelect
body: <p>I don't find a way to remove the first line from my <code>Choices_list</code> which is displayed like <code>-------</code>.</p>
  
  <p>I already tried some things : <code>blank=True</code>, <code>Blank=False</code>, ... and this line is still there.</p>
  
  <p>This is what I'm getting in my Django website :</p>
  
  <p><a href="https://i.stack.imgur.com/eWHDA.png" rel="noreferrer"><img src="https://i.stack.imgur.com/eWHDA.png" alt="enter image description here"></a></p>
  
  <p>My <code>models.py</code> and <code>forms.py</code> files look like :</p>
  
  <pre><code># models.py
  # coding: utf-8
  
  from django.db import models
  from django.utils.encoding import force_text
  
  FAVORITE_THEME = (
      ('Datasystems', 'Datasystems'),
      ('Cameroun', 'Cameroun'),
  )
  
  class Theme(models.Model):
      favorite_theme = models.CharField(max_length = 20, choices=FAVORITE_THEME, verbose_name="Sélectionner le thème")
  
  
  
  # forms.py
  #-*- coding: utf-8 -*-
  
  from django import forms
  from django.forms import ModelForm
  from .models import Theme
  
  class ThemeForm(forms.ModelForm):
      class Meta:
          model = Theme
          widgets = {'favorite_theme' : forms.RadioSelect,}
          fields=('favorite_theme',)
  </code></pre>
  
  <p>Do you have an idea to delete or hide this line ?</p>
  
  <p>Thank you </p>