Invalid attribute values, search console

Hi,

The plugin works correctly but in my console for webmaster this error appears in all publications:

Invalid attribute values: href=//fonts.googleapis.com/css?family=Merriweather:400,400italic,700,700italic%7COpen+Sans:400,700,400italic,700italic

http://www.webyseo.es/como-crear-cuenta-google-analytics-para-novatos/amp

Is there any solution?

Regards

https://wordpress.org/plugins/amp/