fix(Tables): require at least one cell in the header

[max-nextcloud]

📝 Summary

• Resolves: Broken table state #4793.

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• Code is properly formatted (npm run lint / npm run stylelint / composer run cs:check)
• Sign-off message is added to all commits
• hard to test:
  • somewhat complicated to create the state
  • hard to detect it's actually broken.
• Documentation is not required

[max-nextcloud]

/backport to stable28

[max-nextcloud]

/backport to stable27

[max-nextcloud]

/backport to stable26

[max-nextcloud]

After this fix the broken tables below are removed when opening the session again.

[backportbot]

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 backport/5461/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 f7d50b89

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/5461/stable26

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[backportbot]

The backport to stable27 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable27
git pull origin stable27

# Create the new backport branch
git checkout -b backport/5461/stable27

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick f7d50b89

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/5461/stable27

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.