[BUG] Categorical filter in the App sidebar showing erroneous entry

[brimoor]

A user running fiftyone==0.16.5 reports that, when using the filter sidebar in the App on categorical field, an extra erroneous entries appear at the top of the dropdown list.

For example, below we see unknown:

And in the below example, the user states that "100115" means there are 115 results containing 100:

Here's some code I wrote to attempt to reproduce the issue, but I'm not seeing it:

import fiftyone as fo
from fiftyone import ViewExpression as E
from fiftyone import ViewField as F

from bson import ObjectId

# Create 3328 samples with a `group` field
dataset = fo.Dataset()
dataset.add_samples(
    [
        fo.Sample(filepath="/path/to/image.png", group=str(ObjectId()))
        for i in range(3328)
    ]
)

# Ensure at least 115 group values contain "100"
dataset.shuffle().limit(115).set_field("group", E("100").concat(F("group"))).save()

session = fo.launch_app(dataset)