Don’t call dismissNotification if no notification was displayed.

If no update is found and dismissNotification is called with nil an exception is triggered which prevents the update from being aborted. This in turns keeps the Updater process running forever and prevents further update checks from running (when used via launch agent)

[sparkle-project#2]

Sparkle/GPGScheduledUpdateDriver.m

@@ -112,7 +112,17 @@ - (void)didFindValidUpdate {
 }
 
 - (void)abortUpdate {
-    [self dismissNotification:self.updateNotification];
+    // Bug #2: Updater process never exits preventing a new update check from running.
+    //
+    // In case no update is found, `self.updateNotification` is nil and
+    // a call to dismissNotification will trigger an exception within
+    // `[NSUserNotificationCenter removeDeliveredNotification:]`.
+    // Since that exception is not caught, `[super abortUpdate]` which sets the
+    // `finished` flag of the driver is never called and the updater
+    // believes forever that the update is still in progress.
+    if(self.updateNotification) {
+        [self dismissNotification:self.updateNotification];
+    }
     [super abortUpdate];
 }