Pyrogenesis creates empty directories for mods that don't exist

[elexis]

If one launches Pyrogenesis (at least on Ubuntu) with --mod=foo, but mods/foo does not exist, then it will create an empty directory for that and continue.

The application should inform the user that the mod does not exist. If the application would then abort, it could save the user some time until he notices that the mod is disabled.

There may be other circumstances where the empty directory is created:

• whenever a zip/pyromod file is launched?
• whenever a mod is launched?
• Is it created to enable mods config and gui vfs file write access?

I encountered something like 5 directories with mods and 10 empty directories of previously existing or non-existing mods.

[Stan]

Can confirm it does that as well on Microsoft Windows 10.

I believe it does that even if the mod exists, which is the case for the public mod.

[Freagarach]

Duplicate of #5142.