add error checking to Warranty Highlight feature

refactor code

script.js

@@ -1,28 +1,47 @@
 "use strict";
 
 /*
-TODO: insert a reset button into search form
-TODO: style menubar and keep it sticky on the window
-TODO: style/move the location scan to float with the RO
-TODO: implement facebook-style notifications
+	TODO float buttons on bottom of RO
+	TODO float location entry on RO (sidebar?)
+	TODO style individual buttons
+	TODO options page
+		- move parts list buttons top or bottom
+		- color themes?
+	BUG close button on photo pages is styled along with the btnCancel
+	HACK display tiny images next to parts list?
+	TODO shrink navbar/header/location on scroll
+	TODO fancy button animations
+	TODO choose file on upload window
+	TODO insert a reset button into search form
+	TODO style menubar and keep it sticky on the window
+	TODO style/move the location scan to float with the RO
 */
 
 // Warranty Highlight
 const isWarranty = document.getElementById("chkWarrantee");
-isWarranty.addEventListener("change", updateBackground);
-updateBackground();
-function updateBackground() {
-	isWarranty.nextElementSibling.style.backgroundColor = isWarranty.checked
-		? "red"
-		: "transparent";
-	isWarranty.nextElementSibling.style.color = isWarranty.checked
-		? "white"
-		: "black";
+if (isWarranty != null) {
+	isWarranty.addEventListener("change", updateBackground);
+	updateBackground();
+	function updateBackground() {
+		isWarranty.nextElementSibling.style.backgroundColor = isWarranty.checked
+			? "red"
+			: "transparent";
+		isWarranty.nextElementSibling.style.color = isWarranty.checked
+			? "white"
+			: "black";
+	}
 }
 
+// TODO highlight change case label if SN updated
+
+// TODO color bg to bin color
+
+// TODO add current location to top of page somewhere
+
 // Notification system
+// TODO implement facebook-style notifications
 // https://portal.trgrepair.com/task_manager.asp?rnd=0.9996227368620352
 
-const notifCountStr = document.getElementById("lblTask").innerText;
-const notifCount = parseInt(notifCountStr.split(" ")[2]); // Total task count
-const notifCountNew = parseInt(notifCountStr.split(" ")[5].slice(1)); // New task count
+// const notifCountStr = document.getElementById("lblTask").innerText;
+// const notifCount = parseInt(notifCountStr.split(" ")[2]); // Total task count
+// const notifCountNew = parseInt(notifCountStr.split(" ")[5].slice(1)); // New task count