[IRIS] Remove empty IOC in alerts that are not accepted by the API

[gregorywychowaniec-zt]

Description

The IRIS API does not accept a null ioc_value for new alerts : marshmallow.exceptions.ValidationError: {2: {'ioc_value': ['Field may not be null.']}}.

The modification removes IOCs that have no values before send the alert to IRIS.

Checklist

• I have reviewed the contributing guidelines.
• I have included unit tests for my changes or additions.
• I have successfully run make test-docker with my changes.
• I have manually tested all relevant modes of the change in this PR.
• I have updated the documentation.
• I have updated the changelog.

Questions or Comments

[jertel]

Thanks for the submission. We need a unit test showing that the new None check works and then we can get this merged. You can modify test_iris_make_iocs_records and add a third item to the iris_iocs list, where the ioc_value doesn't exist in the match object defined on line 77. That should take care of it.

[gregorywychowaniec-zt]

Sorry, I forgot to add the unit tests. I've added them and tested.