When burnTime is less than or equal to 0, do not process (#5194)

src/main/java/com/gmail/nossr50/listeners/InventoryListener.java

@@ -68,7 +68,7 @@ public class InventoryListener implements Listener {
                 furnaceState instanceof Furnace ? ((Furnace) furnaceState).getInventory()
                         .getSmelting() : null;
 
-        if (!ItemUtils.isSmeltable(smelting)) {
+        if (!ItemUtils.isSmeltable(smelting) || event.getBurnTime() <= 0) {
             return;
         }
 

src/main/java/com/gmail/nossr50/skills/smelting/SmeltingManager.java

@@ -34,6 +34,7 @@ public class SmeltingManager extends SkillManager {
      * @param burnTime The initial burn time from the {@link FurnaceBurnEvent}
      */
     public int fuelEfficiency(int burnTime) {
+        if (burnTime <= 0) return 0;
         return Math.min(Short.MAX_VALUE, Math.max(1, burnTime * getFuelEfficiencyMultiplier()));
     }