Some valid server addresses are not accepted when using -via

[LMattsson]

Describe the bug
When doing a regular login (i.e. not using -via), the following server addresses are allowed in the VNC server input field:

<host>:<port>
<host>::<port>
<host>:<display>

When using -via with <host>::<port> or <host>:<display>, I can log in without any issues. However, using -via with <host>:<port> is not possible and the error message below is shown:

The connection was dropped by the server before the session could be established.

Attempt to reconnect?

To Reproduce
Steps to reproduce the behavior:

1. Run vncviewer -via <host>
2. Input e.g. localhost:5902 in the VNC server field (only one colon)
3. Click connect
4. Enter the password for SSH in the terminal
5. Instead of logging in to TigerVNC, the error message above is shown.

Expected behavior
The same server address should work for login regardless if -via is used or not.

Client (please complete the following information):

• OS: Fedora 39
• VNC client: TigerVNC
• VNC client version: 1.13.1
• Client downloaded from: my Linux distribution

Server (please complete the following information):

• OS: RHEL 9
• VNC server: TigerVNC
• VNC server version: 1.13.1
• Server downloaded from: my Linux distribution
• Server was started using: systemctl start vncserver@:2.service

[CendioOssman]

Fixed in e6d4d3c.