fix(sales invoice): add patient to registration fee sales invoice

(cherry picked from commit aa4a117)

healthcare/healthcare/doctype/patient/patient.py

@@ -317,6 +317,7 @@ def make_invoice(patient, company):
 	uom = frappe.db.exists("UOM", "Nos") or frappe.db.get_single_value("Stock Settings", "stock_uom")
 	sales_invoice = frappe.new_doc("Sales Invoice")
 	sales_invoice.customer = frappe.db.get_value("Patient", patient, "customer")
+	sales_invoice.patient = patient
 	sales_invoice.due_date = getdate()
 	sales_invoice.company = company
 	sales_invoice.is_pos = 0