Fix assertion when picking /UTC out of a date
Fix assertion when picking /UTC out of a date

This corrects for a problem when converting dates to UTC.  It assumes
the desired behavior is something along the lines of:

    d: now
    d/utc = now/utc ;-- approximately true

codebybrett/ren-c,kealist/ren-c,rgchris/ren-c,kealist/ren-c,giuliolunati/ren-c,giuliolunati/ren-c,rgchris/ren-c,codebybrett/ren-c,giuliolunati/ren-c,hostilefork/rebol,draegtun/ren-c,codebybrett/ren-c,codebybrett/ren-c,draegtun/ren-c,draegtun/ren-c,rgchris/ren-c,kealist/ren-c,giuliolunati/ren-c,hostilefork/rebol,kealist/ren-c,giuliolunati/ren-c,kealist/ren-c,draegtun/ren-c,hostilefork/rebol,hostilefork/rebol,rgchris/ren-c,codebybrett/ren-c,codebybrett/ren-c,draegtun/ren-c,kealist/ren-c,rgchris/ren-c,hostilefork/rebol,draegtun/ren-c,hostilefork/rebol