fix: sentry issues (#10695)

1. Ensure audio player ref is accessible before triggering calls
([Sentry](https://chatwoot-p3.sentry.io/issues/6221981610))
2. Use correct default for attachments, this was incorrectly set to
`null` in a previous PR
([Sentry](https://chatwoot-p3.sentry.io/issues/5966738120))
3. Fix `lastNonActivityMessage` is not present
([Sentry](https://chatwoot-p3.sentry.io/issues/6116038455))
4. Fix `Alt+J` & `Alt+K` shortcuts not working
([Sentry](https://chatwoot-p3.sentry.io/issues/6075125384))

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/dashboard/store/modules/conversations/actions.js

@@ -100,7 +100,7 @@ const actions = {
   },
 
   fetchAllAttachments: async ({ commit }, conversationId) => {
-    let attachments = null;
+    let attachments = [];
 
     try {
       const { data } = await ConversationApi.getAllAttachments(conversationId);