[Feature Request] Lint again initial(thing.var), where var is a list

The following code is never correct:

```dm
/datum/species
    var/list/allowed_traits = list(1, 2, 3)

/proc/do_something(datum/species/species_type)
    if (1 in initial(species.allowed_traits))
```

...because lists are made on `init`, the `initial` value is always null.