[SUGGESTION] Make missing textures be replaced in pack-gen with empty image

[Boy0000]

I have checked that...

• [X] ...such a feature does not exist already
• [X] ...such a feature request has not been submitted already

Description

Make the pack-gen make sure a path is correct for fontfiles, and if no textures exist, replace it with required/null.png until it is

Reason

Currently in 1.19 any font-file with a missing texture defined will prevent stuff from loading. Would prevent confusion on why stuff isnt loading, and since the texture doesnt exist anyway theres no real downside