Validate response message for frappe call (#14343)

diff --git a/erpnext/public/js/controllers/buying.js b/erpnext/public/js/controllers/buying.js
index 68bb2b8..bbeb8e9 100644
--- a/erpnext/public/js/controllers/buying.js
+++ b/erpnext/public/js/controllers/buying.js
@@ -236,7 +236,7 @@
 				items: my_items
 			},
 			callback: function(r) {
-				if(r.exc) return;
+				if(r.exc || !r.message) return;
 
 				var i = 0;
 				var item_length = cur_frm.doc.items.length;