When saving project for the first time (or Save as...), other .pxo files are not shown in the selected folder

[hsandt]

Pixelorama version:
v0.11.3-stable

OS/device including version:
Linux Ubuntu 22.04 with Unity desktop

Issue description:
On first save project or Save as..., in the path selection popup, only folders are shown, not files. Since we are saving a file of type .pxo, I expect other .pxo files to be shown (as usual in apps, it allows the user to check for conflicts, and confirm that they are in the correct directory).

Steps to reproduce:

1. Save new project
2. Save as... > popup opens on current file directory which contains at least one .pxo file: the current file we're working on. Yet, the directory appears empty (or only shows subdirs if any)

[OverloadedOrama]

Cannot reproduce on openSUSE Tumbleweed with KDE Plasma 6, unfortunately. It could be a bug with Godot's FileDialog and Unity desktop, but I'm not sure.