No tooltips for `geom_boxplot` with zero height

[OLarionova-HORIS]

Example:

df = {
    'x': ["a"] * 10 + ["b"] * 40,
    'y': [0.2] * 10 + [0.1] * 10 + [0.2] * 20 + [0.3] * 10
}
ggplot(df, aes('x', 'y')) + geom_boxplot()