[BUG] Filter followed by Groupby throws TypeError for categorical column

[rcalland]

Describe the bug
Applying filter followed by a groupby operation causes the following error in my environment:

TypeError: Dtype discrepancy detected for column category_list: operator Groupby reported dtype `int64` but returned dtype `float64`.

Steps/Code to reproduce bug

import pandas as pd
import nvtabular as nvt

# dummy data
_session = ["a", "a", "a", "b"]
_category = ["x", "x", "x", "y"]
_event_type = ["start", "start", "stop", "start"]
input_df = pd.DataFrame(
    {"session": _session, "category": _category, "event_type": _event_type}
)
print(input_df.head())

# graph
cat_feats = ["category"] >> nvt.ops.Categorify()

features = ["session", "event_type"] + cat_feats

# This is the problematic line
features = features >> nvt.ops.Filter(f=lambda df: df["event_type"] == "start")

groupby_features = features >> nvt.ops.Groupby(
    groupby_cols=["session"],
    aggs={
        "category": ["list", "count"],
        "event_type": ["list"],
    },
)

processor = nvt.Workflow(groupby_features)
dataset = nvt.Dataset(input_df)

output_df = processor.fit_transform(dataset)
print(output_df.head())

Expected behavior
The output dataframe should contain nested fields with rows filtered out depending on event_type.

Environment details (please complete the following information):

• Environment location: Bare metal (Apple M1), Python 3.10.9
• Method of NVTabular install: pip (version 1.8.1)

Additional context
I've just started using nvtabular, so its possible I am overlooking something. Would appreciate some help in understanding this error, thanks!