gravatarHash seems not to work anymore

[mantzas]

Using the latest hugo 0.18 seems to have broken the gravatar image since it will not be generated.

[pirxthepilot]

Encountered the same. Fix was to change layouts/partials/sidebar.html from

{{ if isset .Site.Params "gravatarHash" }}

to

{{ if isset .Site.Params "gravatarhash" }}

[liuxueyang]

python code to get hash5