Molecules whose Y size is very small won't display as SVG

[ptosco]

from rdkit import Chem
from rdkit.Chem import Draw
import math
from IPython.display import SVG

smi_list = ["*Cl", "CC"]
mols = [Chem.MolFromSmiles(smi) for smi in smi_list]
sub_size = [250,250]
mols_num = len(mols)
columns_num = 5
rows_num = math.ceil(mols_num/5)
grid = [columns_num,rows_num]
aa = grid[0]*sub_size[0]
ab = grid[1]*sub_size[1]
ac = sub_size[0]
ad = sub_size[1]
d = Draw.rdMolDraw2D.MolDraw2DSVG(aa, ab, ac, ad)
opt = d.drawOptions()
opt.legendFontSize=20
d.SetFontSize(1.3*d.FontSize())
d.SetLineWidth(1)
d.DrawMolecules(mols,
                highlightAtoms=None,
                highlightBonds=None,
                highlightAtomColors=None,
                highlightBondColors=None,
                legends=None)
d.FinishDrawing()
print(d.GetDrawingText())

<?xml version='1.0' encoding='iso-8859-1'?>
<svg version='1.1' baseProfile='full'
              xmlns='http://www.w3.org/2000/svg'
                      xmlns:rdkit='http://www.rdkit.org/xml'
                      xmlns:xlink='http://www.w3.org/1999/xlink'
                  xml:space='preserve'
width='1250px' height='250px' viewBox='0 0 1250 250'>
<!-- END OF HEADER -->
<rect style='opacity:1.0;fill:#FFFFFF;stroke:none' width='1250' height='250' x='0' y='0'> </rect>
<path class='bond-0' d='M 0,250 L 0,250' style='fill:none;fill-rule:evenodd;stroke:#7F7F7F;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1' />
<path class='bond-0' d='M 0,250 L 0,250' style='fill:none;fill-rule:evenodd;stroke:#00CC00;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1' />
<text x='0' y='250' style='font-size:0px;font-style:normal;font-weight:normal;fill-opacity:1;stroke:none;font-family:sans-serif;text-anchor:start;fill:#7F7F7F' ><tspan>*</tspan></text>
<text x='0' y='250' style='font-size:0px;font-style:normal;font-weight:normal;fill-opacity:1;stroke:none;font-family:sans-serif;text-anchor:start;fill:#00CC00' ><tspan>Cl</tspan></text>
<path d='M 0,250 L 0,250 L 0,250 L 0,250 Z' style='fill:none;stroke:#FF0000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;' />
<path class='bond-0' d='M 250,250 L 250,250' style='fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1' />
<path d='M 250,250 L 250,250 L 250,250 L 250,250 Z' style='fill:none;stroke:#FF0000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;' />
</svg>

This is caused by MolDraw2D::setScale setting the scale to 0 if the Y range is < 1e-4, as happens with molecules which are constituted by an horizontal bond and nothing more.