"ipv4.dns-options" and "ipv6.dns-options" are special, in that they can
be either unset/default or an empty list of options. That means, nmcli
must treat these two options differently.
For the (terse) getter, it returns "" for default and " " for empty.
The setter must likewise support and distingish between these two cases.
Cleanup the handling of such options. This only applies to properties of
type "multilist". Hence, add multilist.clear_emptyunset_fcn() handler
that indicates that the property is of that kind.
Try:
nmcli connection modify "$PROFILE" ipv4.dns-options ''
nmcli connection modify "$PROFILE" ipv4.dns-options ' '
and compare the output:
nmcli connection show "$PROFILE" | sed -n '/ipv4.dns-options/ s/.*/<\0>/p'
nmcli -t connection show "$PROFILE" | sed -n '/ipv4.dns-options/ s/.*/<\0>/p'
nmcli -o connection show "$PROFILE" | sed -n '/ipv4.dns-options/ s/.*/<\0>/p'
655a920577