Fix axiom schematics crashing the plot

[BramOtte]

For some reason Axiom uses the version 3 format for the offset but specifies version 2, thus trying to load in a schematic generated by the Axiom mod would crash the plot.

This fixes that by also checking for the Offset property for sponge version 2.

[StackDoubleFlow]

At some point we should also handle cases where those fields don't exist at all. The Sponge Schematic Specification actually specifies Offset to be an optional field with a default of [0, 0, 0]. Also, generally speaking, schematic loading should never crash the plot.

[StackDoubleFlow]

Thanks for fixing this

[StackDoubleFlow]

Actually, Axiom is correct to specificy Offset this way according to the version 2 spec. WorldEdit actually deviates from the spec here, and we were using WorldEdit as the source of truth before. Could you change the comment to not mention Axiom here? I don't want to throw them under the bus for something that isn't their problem.

[BramOtte]

I changed this comment to instead refer to the fact that this is something worldedit specific and that the order of checks matter.
I found out some worldedit generated schematics can have both WEOffset and Offset I think WEOffset is the correct one here but I do wonder why both can be present.

[StackDoubleFlow]

While you're here, could you use if let to check for "Metadata" as well, and then add an else case that just returns (0, 0, 0)

[BramOtte]

The code now checks if one is present for WEOffset and asserts the rest
If neither WEOffset nor Offset are present the default is now (0, 0, 0)

[BramOtte]

I accidentally clicked request review, don't merge this until I have done tests.

[BramOtte]

I have done some rudimentary tests, loading in mpu7, mpu8, iris (various ages of worldedit schematics) and a simple Axiom schematic all seem to load correctly now