Currently, the chain plots crash if maxpoints is larger than the length of the chain. This is because we use a skip variable:
skip = floor(nsimulations / maxpoints)
which gives us spacing so that the sampled points in the plot are evenly distributed across the chain. However, if nsimulations < maxpoints, then skip will be 0, which causes a crash when we try to use it for a range skip.

We fix this by replacing the above line with
skip = max(floor(nsimulations / maxpoints), 1)
so that skip is set to 1 (i.e. the entire chain is plotted) when nsimulations < maxpoints.

To reproduce:

import RATapi as RAT

project, _ = RAT.examples.DSPC_standard_layers()
# broken for any nSamples < 15000 (the default value of maxpoints)
controls = RAT.Controls(procedure="dream", nSamples=1000)

_, results = RAT.run(project, controls)
RAT.utils.plotting.plot_chain(results)
# crash