fix: Ignore groupfolders which have a root_id pointing to nothing

[come-nc]

In case the line in the filecache got lost for some reason (the
directory was deleted and a scan ran, or a deletion crashed mid-way, or
another bug), ignore the groupfolder instead of crashing. We cannot
guess the info from filecache anyway.

• Fix Enabling Groupfolders 20.0.1 on Nextcloud 32.0.0 RC4 (32.0.0.12) - OCP\\Util::numericToNumber(): Argument #1 ($number) must be of type string|int|float, null given #4018

We may want to provide repair steps or cli tools to clean DB in this case, but that’s another subject.

[CarlSchwan]

backport?

[come-nc]

/backport to stable32

[come-nc]

@CarlSchwan right, thanks 🤦

[come-nc]

/backport to stable31

[backportbot]

The backport to stable31 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable31
git pull origin stable31

# Create the new backport branch
git checkout -b backport/4256/stable31

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick b91f4899

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/4256/stable31

Error: Failed to check for changes with origin/stable31: No changes found in backport branch

---

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

[come-nc]

/backport to stable30

[backportbot]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/4256/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick b91f4899

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/4256/stable30

Error: Failed to check for changes with origin/stable30: No changes found in backport branch

---

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