Removed set only once for maintain stock field in item master (#12878)

diff --git a/erpnext/stock/doctype/item/item.js b/erpnext/stock/doctype/item/item.js
index f7250e4..6993187 100644
--- a/erpnext/stock/doctype/item/item.js
+++ b/erpnext/stock/doctype/item/item.js
@@ -110,7 +110,7 @@
 		const stock_exists = (frm.doc.__onload
 			&& frm.doc.__onload.stock_exists) ? 1 : 0;
 
-		['has_serial_no', 'has_batch_no'].forEach((fieldname) => {
+		['is_stock_item', 'has_serial_no', 'has_batch_no'].forEach((fieldname) => {
 			frm.set_df_property(fieldname, 'read_only', stock_exists);
 		});
 	},
diff --git a/erpnext/stock/doctype/item/item.json b/erpnext/stock/doctype/item/item.json
index 7fa4b53..c63d17d 100644
--- a/erpnext/stock/doctype/item/item.json
+++ b/erpnext/stock/doctype/item/item.json
@@ -386,7 +386,7 @@
    "report_hide": 0, 
    "reqd": 0, 
    "search_index": 0, 
-   "set_only_once": 1, 
+   "set_only_once": 0, 
    "unique": 0
   }, 
   {
@@ -3453,7 +3453,7 @@
  "issingle": 0, 
  "istable": 0, 
  "max_attachments": 1, 
- "modified": "2018-01-23 12:21:16.641517", 
+ "modified": "2018-02-12 14:32:48.097249", 
  "modified_by": "Administrator", 
  "module": "Stock", 
  "name": "Item",