fix: fall back to customer id when shopify name and email are missing

[SAY-5]

Issue: customer sync crashes with AttributeError: 'NoneType' object has no attribute 'strip' when a Shopify customer has no first name, last name, or email. In that case customer_name ends up as None and ERPNext rejects it.

Fixes #432

Falls back to Customer {id} so a usable name is always passed through.

[greptile-apps]

Confidence Score: 4/5

Safe to merge if the same fallback is applied to update_existing_addresses; otherwise nameless-customer address updates will persist a blank title.

update_existing_addresses builds customer_name the same way as the code being fixed but has no fallback, so it will still write a whitespace-only address_title for customers with no first/last name.

ecommerce_integrations/shopify/customer.py — update_existing_addresses needs the same fix applied to sync_customer.

_{Reviews (2): Last reviewed commit: "Merge branch 'develop' into fix/shopify-..." | Re-trigger Greptile}

[greptile-apps]

If customer.get('id') is also None the fallback becomes "Customer None". Using or 'Unknown' keeps it explicit, though this edge case is practically impossible with Shopify.

Suggested change

	if not customer_name:
	customer_name = f"Customer {customer.get('id')}"
	if not customer_name:
	customer_name = f"Customer {customer.get('id') or 'Unknown'}"

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!