[Plugin: WordPress SEO by Yoast] Failed to stop the "Google Publisher Page" empty

I’d like to second this – I’m getting a validation error as a result.

Line 50, Column 31: Bad value publisher for attribute rel on element link: Keyword publisher is not registered.

<link rel="publisher" href=""/>

Sorry, this was the bit I meant to copy:

Bad value for attribute href on element link: Must be non-empty.
<link rel="publisher" href=""/>

I’m too. For the moment I delete <link rel="publisher" href="' . esc_attr( $options['plus-publisher'] ) . '"/> from class-frontend.php

Change:

echo '<link rel="publisher" href="' . esc_attr( $options['plus-publisher'] ) . '"/>' . "\n";

To:

if(substr($_SERVER['HTTP_USER_AGENT'], 0, 13) != 'W3C_Validator')
   echo '<link rel="publisher" href="' . esc_attr( $options['plus-publisher'] ) . '"/>' . "\n";
}

in frontend/class-frontend.php