Exception thrown when approvals are being used
This seems to happen when delayed updates are configured.
```
2020-11-13 13:59:48 info updater-supervisor[]: Traceback (most recent call last):
File "/usr/bin/updater-supervisor", line 11, in <module>
load_entry_point('svupdater==1.3.1', 'console_scripts', 'updater-supervisor')()
File "/usr/lib/python3.7/site-packages/svupdater/__main__.py", line 103, in main
File "/usr/lib/python3.7/site-packages/svupdater/_supervisor.py", line 160, in run
File "/usr/lib/python3.7/site-packages/svupdater/_supervisor.py", line 77, in run
File "/usr/lib/python3.7/site-packages/svupdater/approvals.py", line 157, in _approved
TypeError: '>' not supported between instances of 'NoneType' and 'int'
```
issue