actually fix class cast

Author: ghzdude

src/main/java/gregtech/api/items/toolitem/ItemGTToolbelt.java

@@ -76,7 +76,7 @@
 public class ItemGTToolbelt extends ItemGTTool implements IDyeableItem {
 
     private static final ThreadLocal<Integer> lastSlot = ThreadLocal.withInitial(() -> -999);
-    private static final ThreadLocal<EntityPlayer> lastPlayer = ThreadLocal.withInitial(() -> null);
+    private static final ThreadLocal<EntityPlayerMP> lastPlayer = ThreadLocal.withInitial(() -> null);
 
     public ItemGTToolbelt(String domain, String id, Supplier<ItemStack> markerItem, IToolBehavior... behaviors) {
         super(domain, id, -1,
@@ -525,7 +525,7 @@ public static boolean checkIngredientAgainstToolbelt(@NotNull ItemStack input, @
         return false;
     }
 
-    public static void setCraftingSlot(int slot, EntityPlayer player) {
+    public static void setCraftingSlot(int slot, EntityPlayerMP player) {
         lastSlot.set(slot);
         lastPlayer.set(player);
     }

src/main/java/gregtech/mixins/minecraft/ContainerMixin.java

@@ -3,6 +3,7 @@
 import gregtech.api.items.toolitem.ItemGTToolbelt;
 
 import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.inventory.ClickType;
 import net.minecraft.inventory.Container;
 import net.minecraft.item.ItemStack;
@@ -22,8 +23,8 @@ public abstract class ContainerMixin {
     private void setPlayer(int slotId, int dragType, ClickType clickTypeIn, EntityPlayer player,
                            CallbackInfoReturnable<ItemStack> cir) {
         var playerStack = player.inventory.getItemStack();
-        if (playerStack.getItem() instanceof ItemGTToolbelt) {
-            ItemGTToolbelt.setCraftingSlot(slotId, player);
+        if (player instanceof EntityPlayerMP serverPlayer && playerStack.getItem() instanceof ItemGTToolbelt) {
+            ItemGTToolbelt.setCraftingSlot(slotId, serverPlayer);
         }
     }
 }