Filter out empty values for exceptions

[academo]

Summary

Fixes an issue introduced in #102196 where an exception field form can show an empty value when the endpoint doesn't have a value for an exceptionable field.

This PR will remove from the exception list any empty-valued field for memory protection alerts (shellcode and signature)

This same function will later be used for behavior exceptions.

Checklist

Delete any items that are not applicable to this PR.

• Unit or functional tests were updated or added to match the most common scenarios

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/security-onboarding-and-lifecycle-mgt (Team:Onboarding and Lifecycle Mgt)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 3e615d4
• Storybooks Preview

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
securitySolution	6.4MB	6.4MB	+407.0B

History

• 💚 Build #141887 succeeded 73ee896
• 💚 Build #141226 succeeded 5f24903
• 💚 Build #140659 succeeded c0c8c13
• 💚 Build #140647 succeeded b71b1cd

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[kibanamachine]

💚 Backport successful

Status	Branch	Result
✅	7.x

This backport PR will be merged automatically after passing CI.

[kibanamachine]

Looks like this PR has a backport PR but it still hasn't been merged. Please merge it ASAP to keep the branches relatively in sync.