Debug error warning and notice [Notice: Undefined index: token in ]

I am seeing this error Notice: Undefined index: token in public_html/wp-content/plugins/delhivery-logistics-courier/delhivery-logistics-courier.php on line 1881 when I enable debug. It seems to be related to access and need to be resolved asap. Pl suggest changes or update pack. I have updated wordpress 5.8.1 and all other plugin upto date. None of them is causing issue beside this.