Index: build/chrome/ui.js
==================================================================
--- build/chrome/ui.js
+++ build/chrome/ui.js
@@ -84,10 +84,14 @@
 function updateSmartcardReaders(htmlObject) {
 	parentWindow.cackeyListReaders(function(readers) {
 		var idx;
 		var reader;
 		var resultHTML;
+
+		if (!readers) {
+			readers = [];
+		}
 
 		resultHTML = "Count: " + readers.length;
 
 		if (readers.length > 0) {
 			resultHTML += "<br>";