Items which can be unfolded into vehicles cause a crash with ``class JsonError`` if they were mounted on a tool station prior to updating to a version where the item has unfold syntax

[Karol1223]

Describe the bug

You understoof the title? Me neither.

TLDR, in #67047 I gave concrete mixers a use action to unfold them into a vehicle. This works fine for all newly spawned concrete mixers but if a concrete mixer was attached to a tool/kitchen station prior to updating to a version of the game in which concrete mixers can be unfolded, it'll cause a crash upon anyone attempting to activate it.

Attach save file

Edgartown-trimmed.tar.gz

Steps to reproduce

1. Copy the changes from #67047
2. Open the attached savefile
3. On your right you'll have a kitchen station. Detach the concrete mixer from it
4. Attempt to activate the concrete mixer
5. Watch the game crash

Expected behavior

No crashing. Crashing evil.

Screenshots

Versions and configuration

• OS: Windows
  • OS Version: 10.0.22621.3007 (22H2)
• Game Version: 05525e5 [64-bit]
• Graphics Version: Tiles
• Game Language: English [en]
• Mods loaded: [ Dark Days Ahead [dda], Disable NPC Needs [no_npc_food], Portal Storms Ignore NPCs [personal_portal_storms], Slowdown Fungal Growth [no_fungal_growth] ]

Additional context

This may be caused by the fact that the linked PR removes concrete mixers from being able to be attached back onto the tool stations, but I am not certain.

[harakka]

/confirm Merged from linked PR branch to current experimental and followed instructions with the save, crashes as described.

[harakka]

The general cause of this crash is that items don't automatically get all the data from their json definition, if the definition is changed after the item is created. A mixer from prior save doesn't have the foldable vehicle data, and game crashes when trying to access it.

The way to resolve this is to migrate the item using "reset_item_vars": true, this will apply the missing data.

Is this a good enough solution to close this issue? We should probably write this down in migration docs somewhere at least.