851cc07a2a
If the json was empty, for example if the qemu-img command times out, a
message
warn "could not parse qemu-img info command output for '$filename' - $err\n";
would have been printed.
This message could lead one to think the issue lies in the contents of
the json, even if the previous warning said that there was a timeout.
Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>