Replace x() by isset(), !empty() or defaults()

- Remove extraneous parentheses around empty() calls
- Remove duplicate calls to intval(), count() or strlen() after empty()
- Replace ternary operators outputting binary value with empty() return value
- Rewrite defaults() without x()

mod/pubsubhubbub.php

@@ -10,7 +10,7 @@ use Friendica\Util\Network;
 use Friendica\Util\Strings;
 
 function post_var($name) {
-	return (x($_POST, $name)) ? Strings::escapeTags(trim($_POST[$name])) : '';
+	return !empty($_POST[$name]) ? Strings::escapeTags(trim($_POST[$name])) : '';
 }
 
 function pubsubhubbub_init(App $a) {