Fix crashes

tournaments/models/event.py

@@ -20,5 +20,7 @@ class Event(models.Model):
     def display_name(self):
         if self.name:
             return self.name
-        else:
+        elif self.club.name:
             return self.club.name
+        else:
+            return '--'

tournaments/models/tournament.py

@@ -36,7 +36,12 @@ class Tournament(models.Model):
     #estimated_end_date = models.DateTimeField(null=True, blank=True)
 
     def __str__(self):
+        if self.name:
             return self.name
+        elif self.event:
+            return self.event.display_name()
+        else:
+            return '--'
 
     def level(self):
         return self.get_federal_level_category_display()