New zones don't have default TTL applied

[garethhumphriesgkc]

When I create a new zone and push it our to servers, the default TTL isn't populated:

$ cat -A test.zone. | head -5
;$
; This file has been automatically generated using ProBIND v3 on 2021-07-13 02:28:23.$
$
$ORIGIN test.zone.$
$TTL $

I've changed the default TTL to a new value, and can see that value in the database:

mysql> select domain, default_ttl from zones;
+--------------------+-------------+
| domain             | default_ttl |
+--------------------+-------------+
| test.zone          |         300 |
+--------------------+-------------+

To Reproduce
Steps to reproduce the behavior:

1. Create a brand new build as per the build instructions in README.MD
2. Add a server, create a new zone
3. Push changes
4. Check contents of zone file - $TTL line will be missing a number

Expected behavior
TTL should be populated with default TTL value

• OS: Centos 8 (docker-ce)