fix a case where the received notification payload is not valid either for legacy or current PN protocol

SessionMessagingKit/Sending & Receiving/Notifications/PushNotificationAPI.swift

@@ -441,6 +441,7 @@ public enum PushNotificationAPI {
         }
         
         // Only show notifcations for messages from default namespace
+        // TODO: Add group messages namespace
         guard notification.info.namespace == .default else {
             SNLog("Ignoring notification due to namespace being \(notification.info.namespace) instead of default")
             return (nil, notification.info, .failureNoContent)

SessionNotificationServiceExtension/NotificationServiceExtension.swift

@@ -76,7 +76,7 @@ public final class NotificationServiceExtension: UNNotificationServiceExtension
             switch result {
                 // If we got an explicit failure, or we got a success but no content then show
                 // the fallback notification
-                case .success, .legacySuccess, .failure, .legacyFailure:
+                case .success, .legacySuccess, .failure:
                     return self.handleFailure(for: notificationContent, error: .processing(result))
                     
                 // Just log if the notification was too long (a ~2k message should be able to fit so
@@ -92,6 +92,10 @@ public final class NotificationServiceExtension: UNNotificationServiceExtension
                 case .failureNoContent:
                     Log.warn("Failed due to missing notification content.")
                     return self.completeSilenty(handledNotification: false)
+                
+                case .legacyFailure:
+                    Log.warn("Received a notification without a valid payload.")
+                    return self.completeSilenty(handledNotification: false)
             }
         }