fix hysteria faketcp lookback in TUN mode

[Mars160]

在ArchLinux上测试通过
在Android上偶尔会报内存问题，由于对于项目架构不了解，该问题超出了本人能力范围，暂时无法解决

内存部分日志如下

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x644ae845e0]

goroutine 366 [running]:
github.com/Dreamacro/clash/adapter.(*Proxy).URLTest(0x4000506510, {0x644b86fba8?, 0x4000e4c7b0}, {0x4000048690, 0x23}, {0x0?, 0x0, 0x4000526000?}, 0x40000a7e08?)
 github.com/Dreamacro/clash/adapter/adapter.go:290 +0x550
github.com/Dreamacro/clash/adapter/provider.(*HealthCheck).execute.func1()
 github.com/Dreamacro/clash/adapter/provider/healthcheck.go:211 +0x17c
github.com/Dreamacro/clash/common/batch.(*Batch[...]).Go.func1()
 github.com/Dreamacro/clash/common/batch/batch.go:52 +0xec
created by github.com/Dreamacro/clash/common/batch.(*Batch[...]).Go
 github.com/Dreamacro/clash/common/batch/batch.go:43 +0xe0