Empty config settings for vncserver/vncsession can break service

[CendioOssman]

Describe the bug If you specify a setting in one of the vncserver config files, but leave a blank value, then this can for some variables cause the server to fail to start.

To Reproduce Steps to reproduce the behavior:

1. Enter rendernode= in /etc/tigervnc/vncserver-config-defaults
2. Start the vncserver@:#.service

Expected behavior Server is running with DRI3 disabled.

Client (please complete the following information): N/A

Server (please complete the following information):

• OS: RHEL 9
• VNC server: TigerVNC
• VNC server version: 1.14.0
• Server downloaded from: Sourceforge
• Server was started using: sudo systemctl start vncserver@:2.service

Additional context What happens is that rendernode= gets translated to the argument -rendernode=, but it should be translated to -rendernode "". The reason this works for some variables is that the = form is valid for TigerVNC parameters, but not for Xorg arguments (which -rendernode is).

A workaround in this case it to specify some bogus value instead, as that will also disable DRI3.

[CendioOssman]

The issue seems to be the regexp in vncserver:

        if (my ($k, $v) = /^\s*(\w+)\s*=\s*(.+)$/) {

It requires a non-zero number of characters in the value.