allow no privacy notice

smash/web/models/study.py

@@ -96,7 +96,7 @@ class Study(models.Model):
 
     study_privacy_notice = models.ForeignKey("web.PrivacyNotice",
                               verbose_name='Study Privacy Note',
-                              editable=True,
+                              editable=True, blank=True,
                               null=True, on_delete=models.CASCADE, #check cascade ondelete
                               related_name='studies'
                               )