[BUG] JDK25字符串转对象包含非静态内部类时空指针, JDK21正常

### 问题描述
JDK25字符串转对象包含非静态内部类时空指针, JDK21正常

### 环境信息
*请填写以下信息：*

- JDK信息： [e.g.：openjdk version "25.0.3" 2026-04-21 LTS]
- 版本信息：[e.g.：Fastjson2 2.0.62]

### 重现步骤
*如何操作可以重现该问题：*

1. 执行 `main` 方法
2. 出现 `java.lang.NullPointerException` 错误, Summary内部类改成静态内部类或JDK25切回JDK21运行正常

```java
import com.alibaba.fastjson2.JSON;

public class AmzListingJsonFeedResult {

public static void main(String[] args) {
String json = "{\"issues\":[],\"summary\":{\"errors\":0,\"warnings\":0,\"messagesProcessed\":7,\"messagesAccepted\":7,\"messagesInvalid\":0}}";
AmzListingJsonFeedResult result = JSON.parseObject(json, AmzListingJsonFeedResult.class);
System.out.println(result.getSummary().getMessagesAccepted());
}

private Summary summary;

public Summary getSummary() {
return summary;
}

public void setSummary(Summary summary) {
this.summary = summary;
}

public class Summary {
private Integer errors;
private Integer warnings;
private Integer messagesProcessed;
private Integer messagesAccepted;
private Integer messagesInvalid;

public Integer getErrors() {
return errors;
}

public void setErrors(Integer errors) {
this.errors = errors;
}

public Integer getWarnings() {
return warnings;
}

public void setWarnings(Integer warnings) {
this.warnings = warnings;
}

public Integer getMessagesProcessed() {
return messagesProcessed;
}

public void setMessagesProcessed(Integer messagesProcessed) {
this.messagesProcessed = messagesProcessed;
}

public Integer getMessagesAccepted() {
return messagesAccepted;
}

public void setMessagesAccepted(Integer messagesAccepted) {
this.messagesAccepted = messagesAccepted;
}

public Integer getMessagesInvalid() {
return messagesInvalid;
}

public void setMessagesInvalid(Integer messagesInvalid) {
this.messagesInvalid = messagesInvalid;
}
}
}
```

### 期待的正确结果
*无报错*

### 相关日志输出
Exception in thread "main" java.lang.NullPointerException
at java.base/java.util.Objects.requireNonNull(Objects.java:220)
at AmzListingJsonFeedResult$Summary.(AmzListingJsonFeedResult.java:21)
at com.alibaba.fastjson2.reader.ORG_2_5_Summary.readObject(Unknown Source)
at com.alibaba.fastjson2.reader.ORG_1_1_AmzListingJsonFeedResult.readObject(Unknown Source)
at com.alibaba.fastjson2.JSON.parseObject(JSON.java:992)
at AmzListingJsonFeedResult.main(AmzListingJsonFeedResult.java:7)

Run the supplied main method under JDK25 and JDK21 to confirm the difference. Start with the generated reader path shown in the stack trace, com.alibaba.fastjson2.reader.ORG_2_5_Summary.readObject, and inspect how the non-static Summary class is instantiated during JSON.parseObject. Done means the JDK25 run completes without a NullPointerException and prints the accepted-message count.

Written by the indexing model from the issue text.