Combining `geom_histogram` with `geom_linerange` can lead to `AssertionError`

[Vindaar]

The following:

      ggplot(dfIn, aes(dset, fill = "Type")) +
        geom_histogram(bins = 100, hdKind = hdOutline, alpha = 0.5, position = "identity") +
        geom_linerange(aes = aes(x = dM, y = "Dummy", yMin = 0.0, yMax = 100.0)) +
        geom_linerange(aes = aes(x = cM, y = "Dummy", yMin = 0.0, yMax = 100.0)) +
        ggtitle("Property: " & dset & ", Energy: " & $tup[0][1]) +
        ggsave("/t/" & dset & "_compare.pdf")

will lead to an AssertionError in postprocess_scales.nim if the y = "Dummy" is not set. The reason being that histogram does not define a y scale, but geom_linerange is a continuous scale and thus needs a y axis (even though that place is technically taken care of by yMin and yMax'

edit: using such a dummy scale is dumb, as it overwrites the y scale of the geom_histogram as well. This needs to be fixed...

[Vindaar]

eccentricity_compare.pdf

This is what it looks like with the Dummy.