fix: null handling in CLIParser and CombinedCLIParser

[Rohan-Saxena644]

Problem

The CLI XML parser layer has several latent null-pointer vulnerabilities
that can cause silent data corruption or NPEs when processing malformed
XML attachments.

CLIParser.java

• If a <Copyright> node is missing its <Content> child, null is
  silently inserted as a key into the HashMap, which can cause NPEs downstream
• AssessmentSummary missing/multiple element cases were collapsed into
  a single else branch, making it impossible to distinguish between the
  two scenarios in logs

CombinedCLIParser.java

• If a copyright node is missing the srcComponent attribute, externalId
  is null and result.get(null) throws an NPE
• Null contentText values are added to result Sets, polluting downstream data

Fix

PR #3999 addresses all of the above with null guards, split conditionals,
and appropriate log levels.