Problem: WRN could not get window size: The handle is invalid. on Windows

I start my ssh3 server by
```bash
ssh3-server -generate-public-cert myserver.domain -url-path /ssh3 -bind 0.0.0.0:22 -enable-password-login
```
---

When i'm using ssh3 client on windows to connect my Linux server,it shows `WRN could not get window size: The handle is invalid.` and then it stucks.
My command is like this:
```powershell
ssh3 -privkey private_key root@myserver.domain:22/ssh3
```

But it works well on my PC using Arch Linux.
I don't know if it is a bug....

Reproduce the issue with the Windows `ssh3` client command against the shown `ssh3-server` command, then trace the path that emits `WRN could not get window size`. Compare it with the working Arch Linux behavior; done means the Windows client no longer reports the invalid-handle warning or gets stuck during connection.

Written by the indexing model from the issue text.