`TerminateSectors` params extraction may interpret empty array as `null`

### Describe the bug:
We have found a case where the `TerminateSectors` params contained the following:

`{ "Terminations": [] }`

Upon extracting this w lily via `parsed_messages` model, it comes out like this:

`{ "Terminations": null }`

This breaks the consistency of that value always being an array. It should be fixed to properly extract as `{"Terminations": []}` in the exported data.

Example: https://filfox.info/en/message/bafy2bzaceb7ncdapqvbefefczhc63afexfeytxhtgrix7dvk4jyvurribtfk2

### Lily Version: v0.11.0