fix: recognize plate sauce visuals and prevent repeat-application crashes

src/main/java/net/tfminecraft/cooking/manager/PlateManager.java

@@ -89,7 +89,10 @@ public boolean hasSauce(Furniture f) {
             if(!slot.getId().contains("display")) {
                 ItemStack item = slot.getCurrentItem();
                 if(item == null) continue;
+                // addSauce stores an ItemsAdder visual here, without Cooking food metadata.
+                if(slot.getId().equals("sauce")) return true;
                 FoodItem sauce = FoodItem.fromItem(item);
+                if(sauce == null) continue;
                 if(sauce.getCategory().equalsIgnoreCase("sauce")) return true;
             }
         }

src/test/java/net/tfminecraft/cooking/manager/PlateManagerTest.java

@@ -0,0 +1,119 @@
+package net.tfminecraft.cooking.manager;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.UUID;
+
+import org.bukkit.inventory.ItemStack;
+import org.junit.jupiter.api.Test;
+
+import net.tfminecraft.interactiblefurniture.furniture.Furniture;
+import net.tfminecraft.interactiblefurniture.furniture.PlacedSlot;
+
+class PlateManagerTest {
+
+    @Test
+    void unrecognizedItemDoesNotHideLaterSauce() {
+        Map<String, PlacedSlot> slots = new LinkedHashMap<>();
+        Furniture plate = new Furniture("plate", null, UUID.randomUUID()) {
+            @Override
+            public Map<String, PlacedSlot> getActiveSlots() {
+                return slots;
+            }
+        };
+        ItemStack unrecognized = new ItemStack() {
+            @Override
+            public boolean hasItemMeta() {
+                return false;
+            }
+        };
+        PlacedSlot food = new PlacedSlot(plate, "food_item");
+        food.setModel(unrecognized);
+        slots.put("food_item", food);
+        PlacedSlot sauce = new PlacedSlot(plate, "sauce");
+        sauce.setModel(new ItemStack() {});
+        slots.put("sauce", sauce);
+
+        assertTrue(new PlateManager().hasSauce(plate));
+        assertSame(unrecognized, food.getCurrentItem());
+        assertSame(food, slots.get("food_item"));
+    }
+
+    @Test
+    void occupiedSauceSlotCountsAsSauceWithoutFoodMetadata() {
+        Furniture plate = plateWithSauceVisual();
+
+        assertTrue(new PlateManager().hasSauce(plate));
+    }
+
+    @Test
+    void existingSauceReturnsBeforeTouchingThePlayerOrLadle() {
+        Furniture plate = plateWithSauceVisual();
+        ItemStack visual = plate.getActiveSlots().get("sauce").getCurrentItem();
+
+        // Null interaction arguments ensure the duplicate attempt exits before using them.
+        assertDoesNotThrow(() -> new PlateManager().addSauce(null, plate, null, null));
+        assertSame(visual, plate.getActiveSlots().get("sauce").getCurrentItem());
+    }
+
+    @Test
+    void emptySauceSlotDoesNotCountAsSauce() {
+        Furniture plate = new Furniture("plate", null, UUID.randomUUID());
+        plate.getActiveSlots().put("sauce", new PlacedSlot(plate, "sauce"));
+
+        assertFalse(new PlateManager().hasSauce(plate));
+    }
+
+    private Furniture plateWithSauceVisual() {
+        Furniture plate = new Furniture("plate", null, UUID.randomUUID());
+        PlacedSlot sauce = new PlacedSlot(plate, "sauce");
+        sauce.setModel(new ItemStack() {
+            @Override
+            public boolean hasItemMeta() {
+                throw new AssertionError("Sauce visuals must not be parsed as food");
+            }
+        });
+        plate.getActiveSlots().put("sauce", sauce);
+        return plate;
+    }
+
+    @Test
+    void sauceCheckIgnoresUnrecognizedItemsWithoutRemovingThem() {
+        Furniture plate = new Furniture("plate", null, UUID.randomUUID());
+        ItemStack unrecognized = new ItemStack() {
+            @Override
+            public boolean hasItemMeta() {
+                return false;
+            }
+        };
+        PlacedSlot slot = new PlacedSlot(plate, "food_item");
+        slot.setModel(unrecognized);
+        plate.getActiveSlots().put(slot.getId(), slot);
+
+        assertFalse(new PlateManager().hasSauce(plate));
+        assertSame(unrecognized, slot.getCurrentItem());
+        assertSame(slot, plate.getActiveSlots().get("food_item"));
+    }
+
+    @Test
+    void sauceCheckStillIgnoresEmptyAndDisplaySlots() {
+        Furniture plate = new Furniture("plate", null, UUID.randomUUID());
+        PlacedSlot empty = new PlacedSlot(plate, "food_item");
+        plate.getActiveSlots().put(empty.getId(), empty);
+        PlacedSlot display = new PlacedSlot(plate, "display_1");
+        display.setModel(new ItemStack() {
+            @Override
+            public boolean hasItemMeta() {
+                throw new AssertionError("Display items must not be checked for sauce");
+            }
+        });
+        plate.getActiveSlots().put(display.getId(), display);
+
+        assertFalse(new PlateManager().hasSauce(plate));
+    }
+}