Show empty content only when there is nothing to show

[Pytal]

☑️ Resolves

• For Display related resources errors in the panel nextcloud-libraries/nextcloud-vue#3838

Adapt to component changes requested by designers in nextcloud-libraries/nextcloud-vue#3852

Now the panel is visible when there is an error in addition to when there are resources

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not required
• 📘 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

[Pytal]

/backport to stable26

[nickvergessen]

This looks like a wrong approach to me. The problem is that the error occurs, not that it is shown.

Also as you can see it removes the "No shared items" which is not what we want.

[nickvergessen]

The actual problem comes from:

There is an error, but nothing in the logs. So also telling the user to contact the administration is not the right thing to do.

[nickvergessen]

Let's start with finding out what is going on:
nextcloud/related_resources#206

Unluckily I didn't check what the issue was when taking above screenshot and it seems to not always happen

[nickvergessen]

The actual error to fix is at nextcloud/related_resources#207