Fix AttributeError when a File entity has no name or friendlyName

[Copilot]

Sentinel can attach File entities with empty properties, e.g.:

{ "kind": "File", "name": "61127ee5-...", "type": "Microsoft.SecurityInsights/Entities", "properties": {} }

enrich_files assumed a name was always present, so file_field was None and the base module failed with AttributeError: 'NoneType' object has no attribute 'split'.

Changes (modules/base.py)

• Skip nameless file entities: when neither properties.friendlyName nor Name resolves, the entity is skipped, following the same pattern already used for unparseable IP entities in enrich_ips.
• Count after enrichment: FilesCount is now derived from len(base_object.Files) after the loop (previously len(file_entities)), so it stays consistent with the enriched list once entities can be skipped — matching IPsCount.

file_field = data.coalesce(file.get('properties',{}).get('friendlyName'), file.get('Name'))

if not file_field:
    #Skip any file entities that have no file name
    continue

Tests

• tests/test_stat_base.py: added an offline test_enrich_files covering a normal file, an entity with empty properties, and one with a null friendlyName, asserting only the valid entity is enriched and Files/FilesCount agree.

• Fixes AttributeError on file entity missing name and friendlyName #232