Thank you for reporting that.
That 439 line corresponds to this code:
table.insert(player.crafting_categories, "wartime-production")
which is part of the:
for _, player in pairs(data.raw["character"]) do
table.insert(player.crafting_categories, "wartime-production")
end
all it does is go thru all "character" entities and adds them the "wartime-production" category.
The reason why it crashes is simple, there might be a character, which has no crafting category (is set to nil), thus crashing it (why would you want a character that can't craft is beyond me, but maybe some other modder has a really good reason for that)
I could add a simple fix that checks if said character has the crafting category and act accordingly (by only adding the "wartime-production" if it has defined field)
Also can you please do me a favour and tell me which mods are you using too?
I know, "Bob classes" and "Protogen character" loads fine, so I'm curious which mod might be causing that issue.