[6] in 1_plot_maps_mars.ipynb

[rgoalcast]

In Program mars_geology_atlas_of_space/1_plot_maps_mars.ipynb In Part [6]: 

# Plot geologic contacts
savename = './figures/contacts.pdf'
shp = shpreader.Reader(geo_contacts)
fig, ax, ax1, ax2, ax3, ax4 = make_figure()
df = pd.read_csv('./data/Mars_geologic_boundaries.csv', index_col='type')

for record, state in zip(shp.records(), shp.geometries()):
    c = df.loc[record.attributes['ConType']]['color']
    for a in [ax, ax1, ax2, ax3, ax4]:
        a.add_geometries([state], ccrs.PlateCarree(), facecolor='none', edgecolor=c, lw=0.5)

set_save_image(fig, savename)

error : AttributeError: 'NoneType' object has no attribute 'bounds'

How can I remove error ?