Test Case Importer is not using Custom Fields' set Default Value

Description
Test Case Importer is not using Custom Fields' set Default Value, causing the custom field to be set as blank when it should default to the configured default

Pre-conditions
Have a Select Field with a configured Default Value added to Xray's Test Issue Type

How to reproduce

1. Enter TCI and start the Import Process
2. Proceed without mapping the Select List field
3. Finish the Process

Actual result/Attachments
The field is left blank, something that does not happen in Jira's CSV Importer

Expected result
If the field is configured for the Test, the default should be set, as it does in Jira's CSV Importer

Version

• Jira v8.20.x (the improvement to Jira's CSV Importer was made in later Jira versions)