check plots for protection against ggplot change to legend rendering

[zackarno]

just spent an hour trouble shooting why 2 plots in a different repo weren't working as expected.

Therefore, flagging here -- as it could effect any plot aesthetic where we want a legend class to show even if not in the data set (i.e dropped)

tidyverse/ggplot2#5728

[caldwellst]

Have a look through the plotting functions. The only instance where we use factors and legends should be #136. What an annoying change!!

[caldwellst]

Addressed in #146.

[zackarno]

re-opening due to #165

[caldwellst]

This is not related to #165. That is because we have two separate geoms in the legend, and we would rather consolidate into 1.

[zackarno]

it is related as the IPC levels are getting dropped