geom_boxplot: the plot is not drawn if there is a grouping and one of the categories contains only NaN

[ASmirnov-HORIS]

Example:

data = {
    'x': ['a', 'a', 'a', 'b', 'b', 'b', 'c'],
    'y': [0, 1, 2, -1, 0, 1, None],
}
ggplot(data) + geom_boxplot(aes('x', 'y', fill='x'))

Instead of the plot, the message "All data series in data frame must have equal size ..." appears.

Without additional grouping there is no problem, see example:

ggplot(data) + geom_boxplot(aes('x', 'y'))