bug 296202 - typo fix

calendar/base/src/calCalendarManager.js

@@ -266,7 +266,7 @@ calCalendarManager.prototype = {
         // providers (storage and memory). Otherwise we may nuke someone's
         // calendar stored on a server when all they really wanted to do was
         // unsubscribe.
-        if (calendar instanceof Components.interfaces.calICalendarProvider
+        if (calendar instanceof Components.interfaces.calICalendarProvider &&
            (calendar.type == "storage" || calendar.type == "memory")) {
             try {
                 calendar.deleteCalendar(calendar, null);