Plot takes several minutes to show when `scale_color_discrete` is used.

[alshan]

Data: https://drive.google.com/file/d/1mXE8hlzkUh04E0DAdYiZWNtL0Hhc9eae/view?usp=sharing

notebook:

import pandas as pd
from lets_plot import *

LetsPlot.setup_html()

data_enc = pd.read_csv("lets_plot_issue_119.csv")

# !!! This takes several minuts to show plot
ggplot(data_enc) \
        + geom_point(aes('x1', 'x2', color='y')) \
        + scale_color_discrete()

# This is OK
ggplot(data_enc) \
        + geom_point(aes('x1', 'x2', color='y'))

[IKupriyanov-HORIS]

Fixed