CSV import validator does not validate required fields that result in Fatal error during import

Issue Summary

The CSV import validator does not validate required fields.

When the user tried to proceed with the CSV import without required fields, Jira returns a "Fatal error during import".

Steps to Reproduce

1. Configure a required field for an issue type in a project
2. Build a CSV to import that issue type into that project without that required column
3. Validate the import and see Jira finds no issues
4. Proceed with the import and see Jira fails with Fatal error

Expected Results

The validator should warn the user required fields are missing.

Or the error should be more clear as to what caused the error.

Actual Results

Jira fails the import with "Fatal error during import".

The below exception is thrown in the atlassian-jira.log file:

2020-10-20 13:42:32,844-0400 JiraTaskExecutionThread-1909 ERROR username 822x9238993x6 v109gb 10.10.10.10 /secure/ImporterLogsPage%21import.jspa [c.a.j.p.i.i.b.e.BulkCreateDataImporter$ValidableFileImportLoggerThread[https-jsse-nio-8443-exec-9 url:/issues/secure/...Page%21import.jspa username:n1503176,5,main]] Fatal error during import java.lang.NullPointerException at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.doImportIssues(BulkCreateDataImporter.java:235) at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.runImporterEngine(BulkCreateDataImporter.java:172) at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.doImport(BulkCreateDataImporter.java:147)

Workaround

Try to create the same issue type on that same project manually through Jira's interface. See if there's any required field that's not present in the CSV or hasn't been mapped during the import.

Similar to JRASERVER-64670.