[BUG] Folder handle leak

[System233]

I've been using NP3 for many years, and I really enjoy this lightweight editor. Over the years, I've seen many improvements to NP3, but there are a few annoying issues that have been bothering me, so I decided to report them today.

Steps to Reproduce:

1. Use File > Open (ALT+F O) to open any file within a folder.
2. The folder handle for the folder containing the opened file is not released, causing the folder to remain in use and preventing its deletion.
3. Even after opening a new file to close the original file, the folder is still in use.