Handle missing user name in TicketNotesItem to prevent rendering errors

- Use optional chaining for `note.user?.name` in Avatar and text
- Default alt text to empty string if user name is missing
- Show "---" if user name is not available in secondary text
- Prevents runtime errors when `note.user` is undefined
- Improves UI robustness for incomplete note data
- Changes only affect `frontend/src/components/TicketNotesItem/index.js`

Author: allgood

frontend/src/components/TicketNotesItem/index.js

@@ -27,7 +27,7 @@ export default function TicketNotesItem (props) {
     return (
         <ListItem alignItems="flex-start">
             <ListItemAvatar>
-                <Avatar alt={note.user.name} src="/static/images/avatar/1.jpg" />
+                <Avatar alt={note.user?.name || ""} src="/static/images/avatar/1.jpg" />
             </ListItemAvatar>
             <ListItemText
                 primary={
@@ -44,7 +44,7 @@ export default function TicketNotesItem (props) {
                 }
                 secondary={
                     <>
-                        {note.user.name}, {moment(note.createdAt).format('DD/MM/YY HH:mm')}
+                        {note.user?.name || "---"}, {moment(note.createdAt).format('DD/MM/YY HH:mm')}
                     </>
                 }
             />