Repro is with Brim commit 55d1fdc.

Consider the following test data empties.ndjson:

{"empty_object": {}}
{"null_value": null}

When output by Zed CLI tooling, the different nature of the two values is preserved.

$ zq -version
Version: v1.2.0-7-g39539336

$ zq -Z empties.ndjson 
{
    empty_object: {}
}
{
    null_value: null
}

However, when rendered in the Inspector, both values end up looking the same.