reset problem

[Aron Griffis <agriffis@xxxxxxxxx>]

I just noticed something odd.  :reset (or :set &var) doesn't
restore a compile-time default if the default is empty.

    :set smtp_url=foo
    :set ?smtp_url
    smtp_url="foo"
    :reset smtp_url
    :set ?smtp_url
    smtp_url="foo"

Contrast this to a variable that has a non-empty default value:

    :set sendmail=foo
    :set ?sendmail
    sendmail="foo"
    :reset sendmail
    :set ?sendmail
    sendmail="/usr/sbin/sendmail -oem -oi"

Seems like a bug?