[Improve][API] Make sure the table name in TablePath not be null

[Hisoka-X]

Purpose of this pull request

This PR ensure that tablename in TablePath/TableIdentifier is not null, which reduces the burden of downstream processing of null and is more in line with the processing logic in SeaTunnel.

Does this PR introduce any user-facing change?

no

How was this patch tested?

exist test.

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 change log that in connector document. For more details you can refer to connector-v2
  2. Update plugin-mapping.properties and add new connector information in it
  3. Update the pom file of seatunnel-dist
• [ ] Update the release-note.

[Hisoka-X]

cc @hailin0 @hawk9821