Don't cancel previous notification if none existed previously

Bug: 24607839
Change-Id: I2f8737d8ed2101c4572b7570627016a465e3bd44
diff --git a/InCallUI/src/com/android/incallui/StatusBarNotifier.java b/InCallUI/src/com/android/incallui/StatusBarNotifier.java
index 35a22c9..30114b8 100644
--- a/InCallUI/src/com/android/incallui/StatusBarNotifier.java
+++ b/InCallUI/src/com/android/incallui/StatusBarNotifier.java
@@ -269,7 +269,7 @@
          * Fire off the notification
          */
         Notification notification = builder.build();
-        if (mCurrentNotification != notificationType) {
+        if (mCurrentNotification != notificationType && mCurrentNotification != NOTIFICATION_NONE) {
             Log.i(this, "Previous notification already showing - cancelling "
                     + mCurrentNotification);
             mNotificationManager.cancel(mCurrentNotification);