fix code

hutool-core/src/main/java/cn/hutool/core/reflect/NullType.java

@@ -0,0 +1,23 @@
+package cn.hutool.core.reflect;
+
+import java.lang.reflect.Type;
+
+/**
+ * 空类型表示
+ *
+ * @author looly
+ * @since 6.0.0
+ */
+public class NullType implements Type {
+	/**
+	 * 单例对象
+	 */
+	public static NullType INSTANCE = new NullType();
+
+	private NullType(){}
+
+	@Override
+	public String toString() {
+		return "Type of null";
+	}
+}