Error "At least one of ratingCount or reviewCount is required."

[jmastr]

Hi,

first of all great plugin! I really like it!

Initially if you enable the plugin with Google Rich Snippet support and you don't have any reviews yet the markup is not valid:

It says:

• Field ratingValue may not be empty.
• At least one of ratingCount or reviewCount is required.

One solution is to check if score is greater than 0. I will create a PR.