fix: set fg-itm-qty based on qty instead of the other way round i…

…n Subcontracting POs (backport #38842) (#38855)

fix: set `fg-itm-qty` based on `qty` instead of the other way round

(cherry picked from commit a99d0a6)

Co-authored-by: Gughan Ravikumar <gughanrk@gmail.com>

erpnext/buying/doctype/purchase_order/purchase_order.js

@@ -214,15 +214,15 @@ frappe.ui.form.on("Purchase Order Item", {
 		}
 	},
 
-	fg_item_qty: async function(frm, cdt, cdn) {
+	qty: async function (frm, cdt, cdn) {
 		if (frm.doc.is_subcontracted && !frm.doc.is_old_subcontracting_flow) {
 			var row = locals[cdt][cdn];
 
 			if (row.fg_item) {
 				var result = await frm.events.get_subcontracting_boms_for_finished_goods(row.fg_item)
 
 				if (result.message && row.item_code == result.message.service_item && row.uom == result.message.service_item_uom) {
-					frappe.model.set_value(cdt, cdn, "qty", flt(row.fg_item_qty) * flt(result.message.conversion_factor));
+					frappe.model.set_value(cdt, cdn, "fg_item_qty", flt(row.qty) / flt(result.message.conversion_factor));
 				}
 			}
 		}