b27da68320
by not having -W eat the next argument when $scfg->{domain} is defined
but empty.
As reported in the community forum [0], this could lead to issues
adding a storage in the UI.
[0]: https://forum.proxmox.com/threads/44983/post-566842
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>