fix: create contact if existing customer doesn't have contact

(cherry picked from commit 23b0b8ba36)

erpnext/crm/doctype/lead/lead.py

@@ -37,6 +37,15 @@ class Lead(SellingController, CRMNote):
 	def before_insert(self):
 		self.contact_doc = None
 		if frappe.db.get_single_value("CRM Settings", "auto_creation_of_contact"):
+			if self.source == "Existing Customer" and self.customer:
+				contact = frappe.db.get_value(
+					"Dynamic Link",
+					{"link_doctype": "Customer", "link_name": self.customer},
+					"parent",
+				)
+				if contact:
+					self.contact_doc = frappe.get_doc("Contact", contact)
+					return
 			self.contact_doc = self.create_contact()
 
 	def after_insert(self):