F3DColorMapTools::Find does not handle filesystem error correctly

[mwestphal]

Describe the bug
F3DColorMapTools::Find, used to find colormaps is not handling filesystem errors as it should, which can cause issues and unexpected exceptions, eg:

To Reproduce
Steps to reproduce the behavior:

1. Open the file using f3d --colormap-file=folderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolderfolder/file.png
2. catch all triggered

Expected behavior
Better error reporting

System Information:

• OS: Any

F3D Information
Paste the content of f3d --version: 2.5.1 and master

Suggested solution
Adding a try catch around the filesystem usage is a possible solution, but some refactor of the method could be considered.

** Notes **

Same can be said about F3DStarter::SaveScreenshot