Create folders for clips/thumbnails/filmstrips if missing

[TheHardew]

Currently Video Hub App assumes, that the folders that the wizard created will be there when opening the hub, but that does not have to be the case. Before launching ffmpeg make sure that the vha-*/clips folder and simillar actually exist, otherwise the computer will be doing work for no reason, because the generated files will not have anywhere to go.

Ideally this check would run for each file that is being processed or at the very least once before the start of the processing queue.

To recreate:

1. Create a hub using the wizard
2. Go into the hub folder and delete the vha-* folder
3. Video Hub App will not be able to save clips, despite creating them

It's not a huge problem, considering that to recreate this bug a user has to manually edit the files, but considering that creating the clips can take hours, it would be nice, if the program handled this edge case.

I encountered this problem, because I copied the *.vha2 file and edited the path and name inside to manually create a new hub, but I did not create those folders thinking, that they would be created automatically.

[whyboris]

Thank you for the bug report! I took some shortcuts when coding (avoiding handling all the scenarios that I was aware could happen) to save time and effort (so many features to work on - more benefit than an obscure bug) 😅

I should probably add some minor check -- to see if vha-[hub name] exists when opening the .vha2 file 🤔

[TheHardew]

You could extract the folder from args in spawn_ffmpeg_and_run and maybe use fs.mkdir with recursive set to true.