[fix] fix get job metrics get NPE

[liunaijie]

Purpose of this pull request

part fix of https://github.com/apache/seatunnel/issues/8081

Does this PR introduce any user-facing change?

no

How was this patch tested?

exist tests

Check list

• [ ] If any new Jar binary package adding in your PR, please add License Notice according New License Guide
• [ ] If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• [ ] If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config
• [ ] Update the release-note.

[liunaijie]

part of fix, to avoid get NullPointException. We still need find why the running job can't be find in the IMAP