Fixes #6147 - filter both org and env in sys

systems index action does not filter by environment_id when both
organization_id and environment_id are passed; it only filters by
organization_id. This allows the index action to filter by both.
Seems a bit confusing to read. Instead of nil perhaps set to []? then you could do something like
```
env_ids = ... []
env_ids &= ....[]
filters << ..... if env_ids.length > 0
```