Here's a link to the crash report: https://gist.github.com/duely/b559aebc7564e1a7d9ce5c1140c479f5

The context was: I was attempting to sell a number of items as a trade. This was specifically using a series of custom villager recipes (with infinite repetition). The issue appears to be related to https://github.com/MinecraftModDevelopmentMods/Villager-Market/blob/1.12/src/main/java/net/ndrei/villagermarket/VillagerMarketScreen.java#L319

I'm presuming there's a chance for currentRecipe to be null, meaning that the call to to getMaxUses is calling a method on a null variable.

This was resolved by the way, inadvertantly, with the server fix commit.