fix: dont reset UOM in MR on every get_item_detail call (#30164)

diff --git a/erpnext/stock/doctype/material_request/material_request.js b/erpnext/stock/doctype/material_request/material_request.js
index 5f53be0..e68b0ab 100644
--- a/erpnext/stock/doctype/material_request/material_request.js
+++ b/erpnext/stock/doctype/material_request/material_request.js
@@ -214,6 +214,7 @@
 					material_request_type: frm.doc.material_request_type,
 					plc_conversion_rate: 1,
 					rate: item.rate,
+					uom: item.uom,
 					conversion_factor: item.conversion_factor
 				},
 				overwrite_warehouse: overwrite_warehouse
@@ -392,6 +393,7 @@
 	item_code: function(frm, doctype, name) {
 		const item = locals[doctype][name];
 		item.rate = 0;
+		item.uom = '';
 		set_schedule_date(frm);
 		frm.events.get_item_data(frm, item, true);
 	},