wrong lastDbError causes [CBLView removeIndex] fails

In [CBLView removeIndex], _db.lastDbError is returned to the transaction. 

<pre>
    [_db _inTransaction: ^CBLStatus {
        if ([_db.fmdb executeUpdate: @"DELETE FROM maps WHERE view_id=?",
                                     @(_viewID)]) {
            [_db.fmdb executeUpdate: @"UPDATE views SET lastsequence=0 WHERE view_id=?",
                                     @(_viewID)];
        }
        return _db.lastDbError;
    }];
</pre>

While _db.lastDbError does not return correct status, the transaction always fails.