The problem occurred when indexes are added between the time that an
UNDO record is created and the time that the purge thread comes around
and deletes the old secondary index entries.  The purge thread would
hit an assert when trying to build a secondary index entry for
searching.  The problem was that the old value of those fields were not
in the UNDO record since they were not part of an index when the UPDATE
occured. 
A test case was added to innodb-index.test.