Crash on Startup with Railcrafts alternative track recipes

[ThePixelbrain]

The game crashes on launch when Railcraft's alternative track recipes are enabled. They can be enabled in the railcraft/railcraft.cfg config by setting useAltRecipes to true.

Through this config option the Railcraft Track Parts aren't registered by Railcraft. As GT depends on them to create recipes, an invalid recipe with a null output get's generated in this line: https://github.com/Nukepowered/GregTech4/blob/86e83a3fd0e7f6c25b1469995ddf10f9f31bb8f8/src/main/java/gregtechmod/loaders/postload/GT_MachineRecipeLoader.java#L258

Crash report: https://pastebin.com/7LNFHRzs