After updating Graphviz's Docsy (https://gitlab.com/graphviz/graphviz.gitlab.io) to the latest Docsy version, I get this error when running:

WARNING: calling IsSet with unsupported type "invalid" (<nil>) will always return false.                                                                                                                                                                                                                                                                                    

Not very useful, so I added some more logging to track down the caller in gohugoio/hugo#8668, which yields:

WARNING: calling (isset %!q(<nil>) "taxonomycloud") with unsupported collection type "invalid" (<nil>) will always return false.
WARNING: calling (isset %!q(<nil>) "taxonomypageheader") with unsupported collection type "invalid" (<nil>) will always return false.

The culprits:

• https://github.com/google/docsy/blob/master/layouts/partials/taxonomy_terms_clouds.html#L2 which calls {{ if isset .Site.Params.Taxonomy "taxonomycloud" }}
• a few other places calling {{ if isset .Site.Params.Taxonomy "taxonomypageheader" }}

This isn't an error in the output: if taxonomy isn't set in the config.toml, then no taxonomy is output, as expected. But it is a bit of warning noise for older users upgrading, or new users who deleted the taxonomy section.

How about we check if .Site.Params.Taxonomy is defined before looking to see if it has values set inside it?