fixes #327 - event handler for 'page.confirm' always returns true

@@ -1988,8 +1988,10 @@ function createPage(casper) {
         }
     };
     page.onConfirm = function onConfirm(message) {
-        var listener_exists = typeof casper._filters['page.confirm'] !== 'undefined';
-        return listener_exists ? casper.filter('page.confirm', message) : true;
+        if ('page.confirm' in casper._filters) {
+            return casper.filter('page.confirm', message);
+        }
+        return true;
     };
     page.onConsoleMessage = function onConsoleMessage(msg) {
         // client utils casper console message

@@ -13,7 +13,7 @@ casper.start('tests/site/confirm.html', function() {
 
 casper.then(function() {
     //remove the page.confirm event filter so we can add a new one
-    delete casper._filters['page.confirm'];
+    casper.removeAllFilters('page.confirm')
     casper.setFilter('page.confirm', function(message) {
         return false;
     });