The article.html template, when the sharing button is enabled, uses the
description of the page to generate the share link. However the end user
may not want descriptions. If a page description is empty, the following
error is thrown:
```
Error: Failed to build the site
Error: Failed to render page '/home...index.md'
Error: Reason: Failed to render 'article.html'
Error: Reason: Filter call 'urlencode' failed
Error: Reason: Filter `urlencode` was called on an incorrect value: got `null` but expected a String
```
We now check if the description is not empty before passing it to
urlencode, and don't use it if it is not set
176ec48cea