[Minor] Supplier Quotation (#15578)

* throw meaningful error if RFQ does not have selected supplier

* Update supplier_quotation.py

* codacy fix
diff --git a/erpnext/buying/doctype/supplier_quotation/supplier_quotation.py b/erpnext/buying/doctype/supplier_quotation/supplier_quotation.py
index b221a08..5b4356a 100644
--- a/erpnext/buying/doctype/supplier_quotation/supplier_quotation.py
+++ b/erpnext/buying/doctype/supplier_quotation/supplier_quotation.py
@@ -60,7 +60,12 @@
 		for rfq in rfq_list:
 			doc = frappe.get_doc('Request for Quotation', rfq)
 			doc_sup = frappe.get_all('Request for Quotation Supplier', filters=
-				{'parent': doc.name, 'supplier': self.supplier}, fields=['name', 'quote_status'])[0]
+				{'parent': doc.name, 'supplier': self.supplier}, fields=['name', 'quote_status'])
+
+			doc_sup = doc_sup[0] if doc_sup else None
+			if not doc_sup:
+				frappe.throw(_("Supplier {0} not found in {1}").format(self.supplier,
+					"<a href='desk#Form/Request for Quotation/{0}'> Request for Quotation {0} </a>".format(doc.name)))
 
 			quote_status = _('Received')
 			for item in doc.items:
@@ -152,4 +157,4 @@
 		}
 	}, target_doc)
 
-	return doclist
\ No newline at end of file
+	return doclist