The recipe condition for the recipe_unlocked advancement trigger is required, not optional.

How to reproduce:

1. In the launcher, go to the settings and enable "Open output log when Minecraft: Java Edition starts."
2. Launch a modern enough version of Minecraft.
3. Go to the world creation menu.
4. Add the attached datapack to the world.
5. Create the world and look at the log. You will find the error message "Parsing error loading custom advancement manossef:recipe_unlocked: Missing recipe, expected to find a string."

What I expected to happen was:

I could make an advancement that triggers when I get any recipe at all.

What actually happened was:

The recipe condition is required, so the game threw an error in the log when I tried to do that.

Relates to MC-186503.