Revision 1007

Added a section to handle the case where the problem has not yet been
assigned to a user.  This might occur when the problem template is
called form the problem editor before the sets have been assigned
to students.  The problem is obtained as a global problem
then converted to a user_problem with default values.  The problem
is not saved.  This code should be reviewed to make sure there are no
hidden behaviors.  Perhaps a group reading is in order once things
settle down.  This squashes bug #34.
--Mike