fix(lead): don't crash deriving lead name when only ignore_mandatory is set

set_lead_name fell through to email_id.split('@') when a lead had no name,
company or email but ignore_mandatory was set (e.g. data import), raising
AttributeError on a None email. Only derive from email when one exists; the
lead name is then left blank, as intended for that path.

erpnext/crm/doctype/lead/lead.py

@@ -140,7 +140,7 @@ class Lead(SellingController, CRMNote):
 				frappe.throw(_("A Lead requires either a person's name or an organization's name"))
 			elif self.company_name:
 				self.lead_name = self.company_name
-			else:
+			elif self.email_id:
 				self.lead_name = self.email_id.split("@")[0]
 
 	def set_title(self):

erpnext/crm/doctype/lead/test_lead.py

@@ -193,6 +193,29 @@ class TestLead(ERPNextTestSuite):
 		lead.delete()
 		self.assertFalse(frappe.db.exists("Prospect", prospect_name))
 
+	def test_set_lead_name_fallbacks(self):
+		# organization name is used when there is no person name
+		lead = frappe.new_doc("Lead")
+		lead.company_name = "_Test Org Lead"
+		lead.set_lead_name()
+		self.assertEqual(lead.lead_name, "_Test Org Lead")
+
+		# the email local-part is used when only an email is present
+		lead = frappe.new_doc("Lead")
+		lead.email_id = "jane.doe@example.com"
+		lead.set_lead_name()
+		self.assertEqual(lead.lead_name, "jane.doe")
+
+		# data import (ignore_mandatory) with no name/company/email must not crash
+		lead = frappe.new_doc("Lead")
+		lead.flags.ignore_mandatory = True
+		lead.set_lead_name()
+		self.assertFalse(lead.lead_name)
+
+		# otherwise a lead with no name source is rejected
+		lead = frappe.new_doc("Lead")
+		self.assertRaises(frappe.ValidationError, lead.set_lead_name)
+
 
 def create_event(subject, starts_on, reference_type, reference_name):
 	event = frappe.new_doc("Event")