[BUG] Terrain doesn't migrate properly from v9 to v10

[manuelVo]

This is going to be a bug report that's a bit weak - feel free to close it if you aren't interested in investigating further, since it's going to be a temporal issue anyway.

Terrain that was placed on a scene in Foundry v9 doesn't work after a migration to Foundry v10. The terrain will still be placed on the scene, but the cost function won't report any cost for the affected squares. I don't have any good reproduction steps, but I noticed this was happening when I upgraded my dev worlds to v10, and I also got bug reports from other people that were affected by this. manuelVo/foundryvtt-drag-ruler#243