修复：数据生成中不支持处理null的问题

src/main/java/mczme/lingshi/common/utility/ModCodec.java

@@ -0,0 +1,28 @@
+package mczme.lingshi.common.utility;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.OptionalFieldCodec;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.fluids.FluidStack;
+
+import java.util.Optional;
+
+public class ModCodec {
+
+//    序列化工具，可以对null进行处理
+    public static MapCodec<ItemStack> ModoptionalField(final String name, final Codec<ItemStack> codec, ItemStack defaultValue) {
+        return new OptionalFieldCodec<>(name, codec, false).xmap(
+                o -> o.orElse(defaultValue),
+                a -> a==null ? Optional.empty() : Optional.of(a)
+        );
+    }
+
+    public static MapCodec<FluidStack> ModoptionalField(final String name, final Codec<FluidStack> codec, FluidStack defaultValue) {
+        return new OptionalFieldCodec<>(name, codec, false).xmap(
+                o -> o.orElse(defaultValue),
+                a -> a==null ? Optional.empty() : Optional.of(a)
+        );
+    }
+
+}