[Java] Null pointer closing unused JDBC Consumers

It’s legal to create a consumer that you never use, and then on close() vector will be null.

**Reporter**: [Larry White](https://issues.apache.org/jira/browse/ARROW-18179) / @lwhite1

_{**Note**: *This issue was originally created as [ARROW-18179](https://issues.apache.org/jira/browse/ARROW-18179). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

未指定來源檔案或測試。首先重現未使用的 JDBC Consumer 情境，並追蹤其 close() 路徑；完成的標準是，關閉從未使用過的 consumer 不再引發空指標錯誤，並且為該情況提供回歸涵蓋。

由索引模型根據 Issue 內容生成。