fix: 'NoneType' object has no attribute 'stock_uom' (#19532)

diff --git a/erpnext/stock/doctype/pick_list/pick_list.js b/erpnext/stock/doctype/pick_list/pick_list.js
index 3f66743..2789711 100644
--- a/erpnext/stock/doctype/pick_list/pick_list.js
+++ b/erpnext/stock/doctype/pick_list/pick_list.js
@@ -173,8 +173,10 @@
 });
 
 function get_item_details(item_code, uom=null) {
-	return frappe.xcall('erpnext.stock.doctype.pick_list.pick_list.get_item_details', {
-		item_code,
-		uom
-	});
+	if (item_code) {
+		return frappe.xcall('erpnext.stock.doctype.pick_list.pick_list.get_item_details', {
+			item_code,
+			uom
+		});
+	}
 }
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