draw_space only works if there is at least one agent

[quaquel]

Describe the bug
If you try to draw a space and there are no agents in the space, you get an index error

Expected behavior
the space should simply be drawn without any agents

To Reproduce

from mesa.experimental.cell_space import OrthogonalMooreGrid, CellAgent
from mesa import Model
from mesa.visualization import draw_space

model = Model(seed=42)
space = OrthogonalMooreGrid((10,5), random=model.random)

fig, ax = plt.subplots()

draw_space(space, ax=ax)
plt.show()

[EwoutH]

Is this issue still a thing? Suitable for the PyCon sprint?

[Sahil-Chhoker]

This is part of bigger issue I want to tackle with my GSOC project, details are in the comments of #2640.