Trying to update a Hugo theme to work under 0.20.x

After upgrading to hugo 0.20 the theme I have been using on my site no longer builds, and I’m trying to figure out how to fix it.

When running hugo serve I see the following errors

WARNING: Site config's rssURI is deprecated and will be removed in a future release. Set baseName in outputFormats.RSS.
Started building sites ...
WARNING: Page's Now is deprecated and will be removed in a future release. Use now (the template func).
ERROR 2017/04/13 20:18:23 Error while rendering "home": template: theme/index.html:8:7: executing "theme/index.html" at <partial "article_lis...>: error calling partial: template: theme/partials/article_list.html:15:15: executing "theme/partials/article_list.html" at <partial "article_hea...>: error calling partial: template: theme/partials/article_header.html:23:27: executing "theme/partials/article_header.html" at <len .Params.categori...>: error calling len: len of untyped nil
Built site for language en:
0 draft content
0 future content
0 expired content
1 regular pages created
16 other pages created
0 non-page files copied
6 paginator pages created
3 tags created
1 categories created
total in 33 ms
Watching for changes in /home/vendion/pacbsd/hugo-theme-arch/{data,content,static,themes}
Serving pages from memory
Web Server is available at //localhost:1313/ (bind address 127.0.0.1)

The Page’s Now warning has already been fixed on my actual site, but I’m not sure what to do about the “calling len: len of untyped nil” error.

If it helps the theme I’m using is Syui’s hugo-theme-arch

You obviously fixed it in

Re. the first WARNING, update to Hugo 0.20.1.