hostname_max column is empty

Hi,

I'm using pt-query-digest to parse the mysql slow query logs and am trying to visualize the data using anemometer. I run initial DB schema migrations on anemometer, but when I try to run the pt-query-digest command, it fails with the error - `DBD::mysql::st execute failed: Column 'hostname_max' cannot be null`.

The pt-query-digest command -

```
pt-query-digest --user=abc --password=abc --database=slow_query_log \
--review h=localhost,D=slow_query_log,t=global_query_review \
--history h=localhost,D=slow_query_log,t=global_query_review_history \
--no-report --limit=0% slow_query.log
```

I'm running it on mysql version `5.7.12` and percona-toolkit version `2.2.18`.
Any ideas on how to fix it?