If the user hasn't specified a specific template for a workspace, try
to lookup a default one (the empty string).
This allows the user to configure a "fallback" template to be used for
"extra", or not-often-used workspaces.
Gcc (correctly) figured out that we may end up truncating the socket
path. In practice, it's something that should never happen.
Never the less, silence the warning by writing the socket path
directly into the sockaddr_un object.