`layer()` ignores aesthetics

[ASmirnov-HORIS]

Look at the following example:

from lets_plot import *
LetsPlot.setup_html()
ggplot({'x': [0], 'y': [0]}, aes('x', 'y')) + layer('point', size=20, color='red')

It produces the wrong picture, without any aesthetics applied to the point: