Rendre le champs section nullable

speed_rack/backoffice/models.py

@@ -47,7 +47,7 @@ class Reference(models.Model, AdminURLMixin):
     reference_type = models.ForeignKey('ReferenceType', verbose_name='Type')
     title = models.TextField(verbose_name='Titre')
     title_short = models.TextField(verbose_name='Titre court')
-    section = models.CharField(max_length=200, verbose_name='Section')
+    section = models.CharField(max_length=200, blank=True, verbose_name='Section')
     ecli = models.CharField(max_length=200, blank=True, verbose_name='E.C.L.I.')
     url = models.URLField(max_length=200, blank=True)
     comments = models.TextField(blank=True, verbose_name='Commentaires')