Check if the property exists before checking whether it's an int

Older nette/database (pre 3.2.4) used never return type for __get and in that case PHPStan returns "Call to function is_int() with never will always evaluate to true." I could require nette/database 3.2.4 or add this check, and I think the check makes a bit more sense.

Author: spaze

src/MysqlSessionHandler.php

@@ -208,7 +208,7 @@ public function gc(int $max_lifetime): int|false
 		// There is no subtraction on server 1 and one day (or one tenth of $maxLifeTime)
 		// subtraction on server 2.
 		$row = $this->explorer->query('SELECT @@server_id as `serverId`')->fetch();
-		if ($row && is_int($row->serverId) && $row->serverId > 1 && $row->serverId < 10) {
+		if ($row && isset($row->serverId) && is_int($row->serverId) && $row->serverId > 1 && $row->serverId < 10) {
 			$maxTimestamp -= ($row->serverId - 1) * \max(86400, $max_lifetime / 10);
 		}