[Bug]: "Blank page the beginning" adds two pages, one before and one after the beginning

### Preflight Checklist - [x] I have searched the [issue tracker](https://www.github.com/ollm/OpenComic/issues) for a bug report that matches the one I want to file, without success. ### OpenComic Version 1.6.5 ### Operating System Windows 11 ### Installed via .exe ### Steps to reproduce 1. Enable double page mode (Ctrl+D) 2. Enable blank page at the beginning (Ctrl+B) ### Expected Behavior It should add a blank page at the beginning, so instead of having: page1 - page2 | page3 - page4... you should have: blank page - page1 | page2, page3 ### Actual Behavior It adds a blank page before and after the first page, and the layout is: blank page - page1 | blank page - page2 this defeats the whole purpose of this features (shifting the double page) Before (the manga mode is on, but it's the same even it's off): <img width="2559" height="1387" alt="Image" src="https://github.com/user-attachments/assets/b72cd941-dca4-41f3-87cb-6c49b473ac5d" /> After: <img width="2559" height="1386" alt="Image" src="https://github.com/user-attachments/assets/8216fe26-de1b-4256-acb3-6d1e373031c5" /> <img width="2559" height="1390" alt="Image" src="https://github.com/user-attachments/assets/8182f268-c675-4dac-8bb4-eded9a59feb3" /> ### Error message _No response_ ### Additional Information _No response_ ### Sample file _No response_