row_sel_get_clust_rec(), return if a previous version of the clustered index
record does not exist in the read view.  This bug was made and found by
Heikki.  It was harmless as long as the clustered index record contained
a long enough local prefix of externally stored columns, to allow secondary
index records to be built without fetching BLOBs.

InnoDB transactions should never look at a clustered index record whose
transaction identifier (DB_TRX_ID) is not visible in the transaction's
read view.