Merge pull request zo0r#939 from rafaelcamaram/master

Android >= 8.0 is not receiving notifications

Author: zo0r

android/src/main/java/com/dieam/reactnativepushnotification/modules/RNPushNotificationHelper.java

@@ -569,7 +569,8 @@ private void checkOrCreateChannel(NotificationManager manager) {
             }
         }
 
-        NotificationChannel channel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, this.config.getChannelName(), importance);
+        NotificationChannel channel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, this.config.getChannelName() != null ? this.config.getChannelName() : "rn-push-notification-channel", importance);
+
         channel.setDescription(this.config.getChannelDescription());
         channel.enableLights(true);
         channel.enableVibration(true);