fix(tray): GNOME + AppIndicator compatibility

[ivaradi]

The account submenu does not work in a standard (Ubuntu) GNOME environment, for the following reasons:

• If the submenu is empty, no aboutToShow event is sent. This patch pre-populates the submenu.
• If the submenu is updated when handling aboutToShow, it will be closed immediately. This patch causes the event handler to only fetch the activities in this case. It will still enable dynamic updates for KDE, i.e. dataChanged will be called. In case of GNOME, however, the menu is not marked visible, thus the dataChanged handler will not update (and thus close) the menu. However, since the tray menu is built when opening, the contents will be relatively recent even there, though not updating.

Resolves

#10076

Summary

Checklist

• Sign-off message is added to all commits.
• The commit messages are following The Conventional Commits specification.
• The commit history is clean with no merge commits.
  • How to rebase your commits
  • How to squash commits with rebase
• Uploaded screenshots from before and after for UI changes.
• Test(s) added to branch, with before/after results included in PR description, for performance improvements where applicable.
• Documentation has been updated or is not required.
• Backports requested where applicable (critical bugfixes).
• Labels added where applicable (bug/enhancement).
• Milestone added for target version.

AI (if applicable)

• The content of this PR was partly or fully generated using AI
  • I have read the guidelines for AI-assisted contributions.
  • I have read Nextcloud's AI Contribution Policy.

[mgallien]

thanks

[mgallien]

Close #10644

[mgallien]

/backport to stable34.0 please

[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-10646.zip

Digest: sha256:aaa98824c619fb598f7abb3c189ba7a5bee770439e1c165361fd59c99000e13b

To test this change/fix you can download the above artifact file, unzip it, and run it.

Please make sure to quit your existing Nextcloud app and backup your data.

[backportbot]

The backport to stable34.0 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable34.0
git pull origin stable34.0

# Create the new backport branch
git checkout -b backport/10646/stable34.0

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 7b2fbc2a

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/10646/stable34.0

Error: Failed to clone repository: Failed to create working tree: Preparing worktree (new branch 'backport/10646/stable34.0')
fatal: not a valid object name: 'origin/stable34.0'

---

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

[mgallien]

/backport to stable-34.0 please