1.20.4: Recipe changes complain about recipe having air items

[hibiii]

When loading a world, the following lines are emitted in the log:

[14:12:54] [Render thread/ERROR]: Parsing error loading recipe blahaj:blue_shark
com.google.gson.JsonParseException: Item must not be minecraft:air

However, at this point in time, this is unfixable because it requires a large refactor to the way the different versions of the game are handled.