fixed retrive po path in booking controller

updated chinabankslip error message to be more clear
fixed supplier booking report loading button
updated upload invoice frontend to show user po image

app/Http/Controllers/ChinaBankSlipController.php

@@ -68,7 +68,7 @@ class ChinaBankSlipController extends Controller
 
         // TODO: first or fail 
         if(!$china_bankslip){
-            return response()->json(["message"=> "not found"],400);
+            return response()->json(["message"=> "China bankslip not found. Please upload first."],400);
 		}
 		
         $china_bankslip->actual_transfer_amount = $request->input('actual_transfer_amount');