Bugfix: When using ForwardPage(), in FillPage(), previous entry was not given to DoFillPage(). (...)

- Caused by line: ILogEntry lastPrevEntry = Count > 0 ? Entries[Count - 1].Entry : null;
- Line is valid, but Count was reset to 0 in ForwardPage().
- With param lastPrevEntry == null, this caused DoFillPage() to create and append missing lines.
- Count is now reset and returned if MoveNext() fails (eg. no entries left)