Version: X4561
Attempting to set the recipe of a mixer to one that only uses one fluid type crashes the game. (Presumably, a recipe with no fluid types would also crash, but no mixer recipes are fluidless). The issue is probably this line, which tries to access input2's type without checking if input2 is null beforehand:

Crash log: https://pastebin.com/k0Xxc11M

Fixed in X4562