Fix issue where currentChannel was undefined after channel deletion

[Dhanushcdivakar]

This PR addresses the issue where the currentChannel variable was undefined in the CurrentTopicView.vue component when a channel was deleted in another tab while the page was open. It adds a watch on currentChannel to detect when it becomes undefined and implements fallback logic to prevent errors when accessing properties of currentChannel. Manual verification steps included testing the deletion of a channel in one tab while the page remained open in another, ensuring that no errors occurred and the UI reflected the channel's removal properly. This change stabilizes the component by handling the deletion scenario gracefully.

[MisRob]

Hi @Dhanushcdivakar,

the PR description doesn't reflect the code changes, for example

It adds a watch on currentChannel to detect when it becomes undefined and implements fallback logic to prevent errors when accessing properties of currentChannel.

Also, I'd ask you to fill the PR template sections as suggested.