Ensure notification listener is connected before getting notifications

There was a potential race condition where we would try to do a full
refresh of notifications before the listener was connected. Now we
skip the full refresh if we aren't connected, which is fine because
we also do a full refresh in onListenerConnected() anyway.

Bug: 62107069
Change-Id: I2fe4f49eb8a840230d32034be11fe7765a366e75
diff --git a/src/com/android/launcher3/notification/NotificationListener.java b/src/com/android/launcher3/notification/NotificationListener.java
index baaa66a..8121fd5 100644
--- a/src/com/android/launcher3/notification/NotificationListener.java
+++ b/src/com/android/launcher3/notification/NotificationListener.java
@@ -127,8 +127,9 @@
         }
         sNotificationsChangedListener = listener;
 
-        if (sNotificationListenerInstance != null) {
-            sNotificationListenerInstance.onNotificationFullRefresh();
+        NotificationListener notificationListener = getInstanceIfConnected();
+        if (notificationListener != null) {
+            notificationListener.onNotificationFullRefresh();
         }
     }