Show index page instead of hard redirect to 404 on chat delete after signaling error

[ShGKme]

A problem

1. Open a chat
2. Delete the opened chat

Expected behavior

Chat is not open.

Actual behavior

After successful deleting, a web-page received a signaling error and redirect to not-found with a page reload.

🖼️ Screenshots

🏚️ Before

1.mp4

🏡 After

2.mp4

🚧 TODO

• leave room after successful deletion
• Stop waiting for new messages from removed chat
• Push navigation to the root page

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included
• 📘 API documentation in docs/ has been updated or is not required
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required
• 🔖 Capability is added or not needed

[Antreesy]

/backport to stable26

[backportbot-nextcloud]

The backport to stable26 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable26
git pull origin/stable26

# Create the new backport branch
git checkout -b fix/foo-stable26

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts. Resolve them.
git cherry-pick abc123

# Push the cherry pick commit to the remote repository and open a pull request
git push origin fix/foo-stable26

More info at https://docs.nextcloud.com/server/latest/developer_manual/getting_started/development_process.html#manual-backport