Add a checkbox for delete...
UpdateQuery->bindColumn("image", "s", "".(isset($_POST["imageDeleteCheck"])?"":"https://performancehorsehotline.com/files-2021/".$WADAtbl_posts_update->getColumnVal("customerid") ."/". $WA_DFP_UploadStatus["WA_UploadResult1"]["serverFileName"]) ."", "WA_BLANK");
Also update this line:
'DefaultFileName' => "",
to:
'DefaultFileName' => "". (basename($WADAtbl_posts_update->getColumnVal("image",false))) ."",