Vanilla relative teleport doesn't work

CMDBOOK-2152 - Reported by Carl.Fürstenberg

Trying to do the vanilla teleportation doesn't work. i.e. "/tp User ~0 ~4 ~0" returns "Number expected, string received instead"

首先复现 `/tp User ~0 ~4 ~0` 命令，并跟踪 vanilla 对相对传送参数的处理。issue 中未指定文件或测试；完成标准是该命令能够接受相对坐标，且不会出现报告的 “Number expected, string received instead” 错误。

由索引模型根据 Issue 内容生成。