List index out of range on `\dt` command

Found this when testing the 2.0 PR with `dbcli-test` database:

```
Version: 0.15.0
Mail: sqlcli@microsoft.com
Home: http://github.com/dbcli/mssql-cli
dbcli_test> \d "SalesLT"."Product"
list index out of range
dbcli_test>
```

it's also broken in master, so not related to the prompt-toolkit upgrade.