Our App Studio test suite caught an issue with this code in the latest RC of plotly.py:

df = pd.DataFrame({
  'x': [],
  'y': [],
})
fig = px.bar(df, x="x", y="y")

In v5.24.1, this produces an empty graph as expected
In v6.0.0rc0, this raises an Exception: ValueError: zero-size array to reduction operation maximum which has no identity

This is a simple case, but a more realistic use case would be when a dataframe is filtered down to nothing due to user input.