I have checked on your site and can see the problem, it is a different issue than described in the erratum.
I tried to reproduce the same problem on a local test site but could not, the add community form works normally even when Toolset plugins (specifically Views) is active, so I have taken a copy of your site to test locally.
I can see the problem on the local version of your site, so I will conduct further testing there to see if I can identify the cause.
I can't see why, but I identified the problem as arising from the Toolset Content Template "Template for Beiträge", which is an unused, empty template.
Having trashed the template, the community add page works as expected, both on my local copy of your site, and also on your staging site.
Can you please try the same on your production site, I expect that will fix it.