Duplicate unfilled shapes

[bersbersbers]

In 0.7.1, this code produces identical shapes for data points 03-06 as for 10-13:

"""Bug."""
import pandas as pd
from plotnine import aes, geom_point, ggplot, scale_shape

p = ggplot(pd.DataFrame([f"{i:02}" for i in range(14)], columns=["x"]))
p = p + aes(x="x", y=0, shape="x") + geom_point() + scale_shape(unfilled=True)
p.save("bug.png")

Package versions are as in #472.

[bersbersbers]

Thanks!