[Bug] Cannot load saved games from older TRX versions

### Game type Not sure ### Game TR1 ### TRX version 1.8.1 ### Operating system Debian Linux ### GPU _No response_ ### Describe the bug in plain terms, and write the shortest steps that reproduce it. I cannot load all of my saved games. I have saved the first 8 levels but only the latest 3 will load, the rest return me to the title screen. The saved games have been saved with various TRX versions. In a hex editor, some start with T1MB and newer start with TRXS. Is it not possible to load the old saves any more, and can they be converted? ### What did you expect instead? I expected them to load. ### Attachments None. ### Before submitting - [x] I included enough detail to reproduce this. - [x] I attached `TRX.log` and any saves, media, or custom level files needed to reproduce this. - [x] This issue covers one bug.