"Delete this and later bids" does not correctly refer to the remaining highest bid

Problem/Motivation

Deleting bids does not correctly populate the high_bid value in uc_auction table with the remaining highest bid.

Proposed resolution

Patch in comment#2.

Remaining tasks

Verify and commit.

Additional notes

Related issue: #390908: "Delete this and later bids" doesn't work with double digit BID's. It may be the difference of db query function between d6 & d7, where in d7 fetchField() method directly returns the value rather than an array.