I think the create_inits function (here) needs to replace the line pareto_smooth(w, tail='right', r_eff=1)$x with just pareto_smooth(w, tail='right', r_eff=1). According to the most recent posterior documentation, pareto_smooth will only return diagnostics along with x if extra_diags is set to TRUE and it is FALSE by default.
I think the create_inits function (here) needs to replace the line
pareto_smooth(w, tail='right', r_eff=1)$xwith justpareto_smooth(w, tail='right', r_eff=1). According to the most recent posterior documentation,pareto_smoothwill only return diagnostics along withxifextra_diagsis set toTRUEand it isFALSEby default.