Small optimisation

js/modules/loki_message_api.js

@@ -169,11 +169,11 @@ class LokiMessageAPI {
         incomingHashes
       );
       const newMessages = messages.filter(m => !dupHashes.includes(m.hash));
+      if (newMessages.length) {
         const newHashes = newMessages.map(m => ({
           expiresAt: m.expiration,
           hash: m.hash,
         }));
-      if (newHashes.length) {
         await window.Signal.Data.saveSeenMessageHashes(newHashes);
       }
       return newMessages;