fix: Catch not found card

[juliusknorr]

The find method may throw an exception that we can just handle as no permission

Fixes #6516

[juliusknorr]

/backport to stable30

[juliusknorr]

/backport to stable29

[backportbot]

The backport to stable29 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable29
git pull origin stable29

# Create the new backport branch
git checkout -b backport/6646/stable29

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick a35489be

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/6646/stable29

Error: No changes found in backport branch

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