fix: lead name issue (#26999)

* fix: lead name issue

* fix: change lead name wrt first name, middle and last name

Co-authored-by: Jannat Patel <31363128+pateljannat@users.noreply.github.com>

erpnext/crm/doctype/lead/lead.py

@@ -36,7 +36,8 @@ class Lead(SellingController):
 		})
 
 	def set_full_name(self):
-		self.lead_name = " ".join(filter(None, [self.first_name, self.middle_name, self.last_name]))
+		if self.first_name:
+			self.lead_name = " ".join(filter(None, [self.first_name, self.middle_name, self.last_name]))
 
 	def validate_email_id(self):
 		if self.email_id: