(src/feed.njk) Error: Collection is empty in rssLastUpdatedDate filter

[yaaax]

Hi there,

First of all thank you so much for this great starter kit, beautifully integrated !
I'm a big fan of Andy Bell's work ;)

I get this error after remove all example posts and building (through netlify or locally even with npm start) :
Problem writing Eleventy templates: (more in DEBUG output)

> Having trouble rendering njk template ./src/feed.njk
> `TemplateContentRenderError` was thrown
> (./src/feed.njk)
   Error: Collection is empty in rssLastUpdatedDate filter.

It looks like an easy issue to fix, I'll do a Pull Request in 5 mn :)