Link item shouldn't be null.

Author: zenfyrdev

src/main/java/com/github/vini2003/linkart/mixin/AbstractMinecartEntityMixin.java

@@ -125,7 +125,7 @@ public AbstractMinecartEntityMixin(EntityType<?> type, World world) {
 
         linkart$spawnChainParticles((AbstractMinecartEntity) (Object) this, this);
 
-        duck.linkart$setLinkItem(null);
+        duck.linkart$setLinkItem(ItemStack.EMPTY);
     }
 
     @Inject(at = @At("HEAD"), method = "pushAwayFrom", cancellable = true)
@@ -198,6 +198,6 @@ void onPushAway(Entity entity, CallbackInfo ci) {
 
     @Override
     public void linkart$setLinkItem(ItemStack linkItem) {
-        this.linkart$itemStack = linkItem;
+        this.linkart$itemStack = linkItem == null ? ItemStack.EMPTY : linkItem;
     }
 }

src/main/java/com/github/vini2003/linkart/mixin/PlayerEntityMixin.java

@@ -65,7 +65,7 @@ void onInteract(Entity entity, Hand hand, CallbackInfoReturnable<ActionResult> c
 
                                 linkart$spawnChainParticles(minecart, duck);
 
-                                duck.linkart$setLinkItem(null);
+                                duck.linkart$setLinkItem(ItemStack.EMPTY);
 
                                 cir.setReturnValue(ActionResult.SUCCESS);
                             } else {