fix: Update the logic to handle attachments in a conversation (#9784)

When the chat is viewed, a function `fetchAllAttachments` is run to get all attachments for a particular conversation. This function, before updating the record creates the `attachments` property on the `chat` object in the store.
If in any case this function fails, the `attachments` property is not created, and when the code reaches the `dashboard/store/modules/conversations/index.js` the error occurs

This PR fixes it by ensuring that `SET_ALL_ATTACHMENTS` is always run. And it handles the default case as well


---

Sentry Issue:
[CHATWOOT-FRONTEND-APP-5Y](https://chatwoot-p3.sentry.io/issues/5459056982/)

```
TypeError: Cannot read properties of undefined (reading 'some')
  at forEach(./app/javascript/dashboard/store/modules/conversations/index.js:160:31)
  at Array.forEach(<anonymous>)
  at mutations(./app/javascript/dashboard/store/modules/conversations/index.js:159:27)
  at handler(./node_modules/vuex/dist/vuex.js:771:7)
  at forEach(./node_modules/vuex/dist/vuex.js:470:9)
  at Array.forEach(<anonymous>)
  at fn(./node_modules/vuex/dist/vuex.js:469:13)
  at Store.prototype._withCommit(./node_modules/vuex/dist/vuex.js:574:5)
  at Store.prototype.commit(./node_modules/vuex/dist/vuex.js:468:10)
  at this.commit(./node_modules/vuex/dist/vuex.js:420:21)
  at call(./app/javascript/dashboard/store/modules/conversations/actions.js:273:7)
  at tryCatch(./node_modules/videojs-record/dist/videojs.record.js:2868:27)
  at _invoke(./node_modules/videojs-record/dist/videojs.record.js:3088:32)
  at prototype[method](./node_modules/videojs-record/dist/videojs.record.js:2921:31)
  at as(/packs/js/application-cf716bca3c984faeb095.js:4:76)
  at as(/packs/js/application-cf716bca3c984faeb095.js:4:76)
  at nrWrapper(/app/accounts/81898/conversations/95:6:17817)
```

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>
Co-authored-by: Pranav <pranav@chatwoot.com>

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

@@ -18,9 +18,8 @@ const getters = {
     );
     return selectedChat || {};
   },
-  getSelectedChatAttachments: (_state, _getters) => {
-    const selectedChat = _getters.getSelectedChat;
-    return selectedChat.attachments || [];
+  getSelectedChatAttachments: ({ selectedChatId, attachments }) => {
+    return attachments[selectedChatId] || [];
   },
   getChatListFilters: ({ conversationFilters }) => conversationFilters,
   getLastEmailInSelectedChat: (stage, _getters) => {