It seems like CD-ROMs may have no 'fileName' property specified in case
there is nothing configured as attachment for the drive. Hence, make
sure that virVMXParseDisk() do not consider it mandatory anymore,
considering it an empty block cdrom device. Sadly virVMXParseDisk() is
used also to parse disk and floppies, so make sure that a NULL fileName
is handled in cdrom- and floppy-related paths.

https://bugzilla.redhat.com/show_bug.cgi?id=1808610Signed-off-by: NPino Toscano <ptoscano@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Tested-by: NRichard W.M. Jones <rjones@redhat.com>