Fit functionality not working for *_density plots

[rancesol]

Following the example the fit is not created.

That is to say, running scaling.mass_density_metrics(cat1, cat2, 'cross', ax_rotation=45, add_fit=True, fit_bins1=8) should produce a density plot of the mass-mass plane with a binned fit (showing the binned points and the best fit line + error) and metric subplots. However, the binned fit is missing.

The fit does show up if you run scaling.mass(cat1, cat2, 'cross', ax_rotation=45, add_fit=True, fit_bins1=8). Likewise, the same issue is seen in the redshift equivalent versions of these functions.