Fix generating etherpad links

/close #63

models/database.py

@@ -226,15 +226,13 @@ class Protocol(DatabaseModel):
         return "Protokoll:{}-{:%Y-%m-%d}".format(self.protocoltype.short_name, self.date)
 
     def get_etherpad_link(self):
-        print(self.pad_identifier)
-        if self.pad_identifier is not None:
-            return self.pad_identifier
+        if self.pad_identifier is None:
             identifier = self.get_identifier()
             if self.protocoltype.non_reproducible_pad_links:
                 identifier = "{}-{}".format(identifier, str(uuid4()))
             self.pad_identifier = identifier
             db.session.commit()
-        return get_etherpad_url(identifier)
+        return get_etherpad_url(self.pad_identifier)
 
     def get_datetime(self):
         return datetime(self.date.year, self.date.month, self.date.day, self.protocoltype.usual_time.hour, self.protocoltype.usual_time.minute)