Let PAGES.GroupByParam return nil instead of error

[jmooring]

Typical construct:

{{ range site.Pages.GroupByParam "foo" }}
  <h2>{{ .Key }}</h2>
  {{ range .Pages }}
    <h3><a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a></h3>
  {{ end }}
{{ end }}

For an existing site where one or more of the pages contains params.foo in front matter, this works great.

But if none of the pages contains params.foo in front matter, the GroupByParam method throws this error:

error calling GroupByParam: there is no such param

I think we should return nil instead. Reasoning:

1. Symmetry
   • Pages.SortByParam doesn't complain about missing param
   • Pages.GroupByParamDate doesn't complain about missing param
2. Avoid dead ends. For example, a new empty site when a theme contains a construct similar to the above.

Reference: https://discourse.gohugo.io/t/error-calling-groupbyparam-there-is-no-such-param/50205

[bep]

Agree.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.