[ic] Bug found: get_cart with merge=1

[brian at vermonster.com]

Hello,

I am on IC 5.2 and think I've discovered a bug with the userdb get_cart function
with the merge="1" flag.

Consider a saved cart consisting of a master item with one or more sub-items.  A
user imports this saved cart twice.  Deleting one of the master items causes
all the sub-items are deleted.

I looked in the [dump] and noticed that the mv_mi id's for the two groups are
the same.  It seems that get_cart with merge="1" does not consider the mv_mi
values of items already in the shopping cart.  It should and I believe this is
a bug.

- Brian