Code review comment for lp:~tkluck/simple-scan/autosaves

Did the following:
0. $ ~/.cache/simple-scan/autosaves/autosaves.db
1. $ simple-scan test
2. Pressing scan
3. Ctrl+C
4. $ simple-scan

It worked some times but not always. The log from a failure is:
[+0.00s] DEBUG: simple-scan.vala:582: Starting Simple Scan 3.6.0, PID=11515
[+0.00s] DEBUG: Connecting to session manager
[+0.04s] WARNING: g_object_set_valist: invalid object type `GtkAdjustment' for value type `GtkWidget'
[+0.04s] DEBUG: ui.vala:1463: Restoring window to 774x607 pixels
[+0.04s] DEBUG: autosave-manager.vala:87: creating a new instance of the autosave manager
[+0.04s] DEBUG: autosave-manager.vala:220: Executing query "
            CREATE TABLE IF NOT EXISTS pages (
                id integer PRIMARY KEY,
                process_id integer,
                page_hash integer,
                book_hash integer,
                book_revision integer,
                page_number integer,
                dpi integer,
                width integer,
                height integer,
                depth integer,
                n_channels integer,
                rowstride integer,
                color_profile string,
                crop_x integer,
                crop_y integer,
                crop_width integer,
                crop_height integer,
                scan_direction integer,
                pixels binary
            )"
[+0.06s] DEBUG: autosave-manager.vala:117: preparing query "
                   SELECT process_id, book_hash, book_revision FROM pages
                   WHERE NOT process_id IN (11515)
                   LIMIT 1
                "
[+0.06s] DEBUG: autosave-manager.vala:123: found at least one autosave page, taking ownership
[+0.06s] DEBUG: autosave-manager.vala:139: Executing query "
                        UPDATE pages
                           SET process_id = 11515
                         WHERE process_id = 11505
                           AND book_hash = -671049168
                           AND book_revision = 0"
[+0.06s] DEBUG: autosave-manager.vala:404: preparing query "
            SELECT process_id,
                page_hash,
                book_hash,
                book_revision,
                page_number,
                dpi,
                width,
                height,
                depth,
                n_channels,
                rowstride,
                color_profile,
                crop_x,
                crop_y,
                crop_width,
                crop_height,
                scan_direction,
                pixels,
                id
            FROM pages
            WHERE process_id = 11515
              AND book_revision = (
                  SELECT MAX(book_revision) FROM pages WHERE process_id = 11515
              )
            ORDER BY page_number
        "
[+0.06s] DEBUG: autosave-manager.vala:474: no pages found to recover
[+0.06s] DEBUG: autosave-manager.vala:57: setting book to autosave
[+0.06s] DEBUG: autosave-manager.vala:72: connecting to signals of new book
[+0.10s] DEBUG: scanner.vala:1419: sane_init () -> SANE_STATUS_GOOD
[+0.10s] DEBUG: scanner.vala:1425: SANE version 1.0.23
[+0.10s] DEBUG: scanner.vala:1486: Requesting redetection of scan devices
[+0.10s] DEBUG: scanner.vala:776: Processing request
[+2.52s] DEBUG: scanner.vala:338: sane_get_devices () -> SANE_STATUS_GOOD
[+5.06s] DEBUG: autosave-manager.vala:176: clean exit; deleting autosave records
[+5.07s] DEBUG: scanner.vala:1559: Stopping scan thread
[+5.07s] DEBUG: scanner.vala:776: Processing request
[+5.07s] DEBUG: scanner.vala:1567: sane_exit ()

The database is http://ubuntuone.com/7K3prqGhNEgBslU2BQ8Ckh