Document Caches do not populate the first time you load into a new world

[akrigline]

Core v10.291
system commit 0e11047

Reproduction Steps:
0. Have black-flag system and black-flag-content module installed

1. Create a new world with the black-flag system
2. Create a new character
3. Observe "Lineage", "Heritage", etc dropdowns.

Expected: These should be populated
Actual: The dropdowns are empty

Looking at CONFIG.SYSTEM I see the Maps exist, but are empty.

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This does not happen if you return to setup and then come back.
Is it possible that Foundry Core does not have the content module active when init for the system prepares the document caches?

This does not reproduce if you remove all actors from the world, reload (or return to setup and come back), and then create a new character.

[akrigline]

Ok, it's getting wierder, the compendium packs are all empty on this first world load.

So that's definitely the culprit.
game.packs.get("black-flag-content.backgrounds").index is an empty collection
game.packs.get("black-flag-content.backgrounds").getIndex() doesn't appear to fix it

But simply reloading does.

Starting to suspect this is a Core Bug