Template: Explicitly set full as the default custom logo size.

See #33755.


git-svn-id: https://develop.svn.wordpress.org/trunk@36950 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/general-template.php

@@ -878,6 +878,10 @@ function get_custom_logo( $blog_id = 0 ) {
 	$custom_logo_id = get_theme_mod( 'custom_logo' );
 	$size           = get_theme_support( 'custom-logo', 'size' );
 
+	if ( ! $size ) {
+		$size = 'full';
+	}
+
 	// We have a logo. Logo is go.
 	if ( $custom_logo_id ) {
 		$html = sprintf( '<a href="%1$s" class="custom-logo-link" rel="home" itemprop="url">%2$s</a>',