事物回滚报空指针异常

- [ ] I have searched the [issues](https://github.com/codingapi/tx-lcn/issues) of this repository and believe that this is not a duplicate.

### 1. Bug Description
类 TransactionControlTemplate，传入到DefaultDTXExceptionHandler中的ex是空的
这里调用会报空指针

### 2. Environment:
- JDK version:
- OS:
- TX-LCN version:
- Others:

### 3. Exception Stacktrace

```
Paste your Exception Stacktrace here!
```

### 4. Tour Idea

Start by tracing the rollback path from TransactionControlTemplate into DefaultDTXExceptionHandler, where the issue reports that ex is null. Reproduce the rollback failure using the reported scenario and inspect the available stack trace or surrounding handling logic. Done means rollback no longer causes a null-pointer exception, with regression coverage if an existing test location can be identified.

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