Referencing Variable before it exists

[WildSecurity]

Hello Everyone,

I've noticed the following two code Fragments:
if not date_modified: at line 157
https://github.com/atc-project/atomic-threat-coverage/blob/master/scripts/es_index_export.py#L157
if not date_created: at line 136
https://github.com/atc-project/atomic-threat-coverage/blob/master/scripts/es_index_export.py#L136

My python skills are negligable, but I think it should be
if not "date_modified" in locals() or something like this.
Otherwise python will crash because it is trying to access a variable which may not be assigned.

If I would be more proficient in git, I would send a merge request, but I hope this is good enough.

Regards,

Linus