Ensure that ?author=0 resolves to blog user (#996)

Author: mattwiebe

includes/functions.php

@@ -199,10 +199,7 @@ function url_to_authorid( $url ) {
 
 	// First, check to see if there is a 'author=N' to match against.
 	if ( \preg_match( '/[?&]author=(\d+)/i', $url, $values ) ) {
-		$id = \absint( $values[1] );
-		if ( $id ) {
-			return $id;
-		}
+		return \absint( $values[1] );
 	}
 
 	// Check to see if we are using rewrite rules.