The coin bag works perfectly fine in survival but if you are in creative and you are burning iron and/or steel and have no nuggets in your inventory the bag doesn't throw a coin/nugget but I think it does try to make a blue line follow it but since there was no coin to follow Minecraft crashes with a null pointer.
So I think there needs to be a check on the right click event for the coin bag that even in creative it won't work if you have no coins on you, that would fix the crash issue.
The coin bag works perfectly fine in survival but if you are in creative and you are burning iron and/or steel and have no nuggets in your inventory the bag doesn't throw a coin/nugget but I think it does try to make a blue line follow it but since there was no coin to follow Minecraft crashes with a null pointer.
So I think there needs to be a check on the right click event for the coin bag that even in creative it won't work if you have no coins on you, that would fix the crash issue.