pairplot fails with hue_order not containing all hue values in seaborn 0.11.1

In seaborn < 0.11, one could plot only a subset of the values in the hue column, by passing a hue_order list containing only the desired values. Points with hue values not in the list were simply not plotted.

iris = sns.load_dataset("iris")`
# The hue column contains three different species; here we want to plot two
sns.pairplot(iris, hue="species", hue_order=["setosa", "versicolor"])

This no longer works in 0.11.1. Passing a hue_order list that does not contain some of the values in the hue column raises a long, ugly error traceback. The first exception arises in seaborn/_core.py:

TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

seaborn version: 0.11.1 matplotlib version: 3.3.2 matplotlib backends: MacOSX, Agg or jupyter notebook inline.

[mwaskom]

Easiest workaround is probably

hue_order = ["setosa", "versicolor"]
sns.pairplot(iris.query("species in @hue_order"), hue="species", hue_order=hue_order)

[mwaskom]

Closed with #2848