FROM SUBSELECT
ISSUE         : In function find_all_keys.
                If selected row do not satisfy condition
                then we call unlock_row to release the locked
                row. Suppose if we have subquery in condition
                and we have an innodb error during its execution.
                Then we should not call the unlock_row. If the error
                is because of deadlock, innodb will rollback the
                transaction. And calling unlock_row without
                transaction is an invalid case hence an assertion
                failure.
SOLUTION      : We call unlock_row only if only there is no
                error occurred previously.
                The solution is back ported from 5.6
                defect number 14226481