[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.*}

No source file or test is named. Start by reproducing the unused JDBC Consumer scenario and tracing its close() path; done means closing a consumer that was never used no longer raises a null-pointer error, with regression coverage for that case.

Written by the indexing model from the issue text.