fix: frontend errors

[faelau]

This PR fixes some error that provokes an error on various widgets if a service is in the state pending or has no parent.

Please feel free to edit the PR if the submitted code does not conform with your internal coding guidelines.

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[cla-bot]

Thank you for your pull request. Before we can look at it, you'll need to sign a Contributor License Agreement (CLA).

Please follow instructions at https://icinga.com/company/contributor-agreement to sign the CLA.

After that, please reply here with a comment and we'll verify.

Contributors that have not signed yet: @faelau

Details

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Please contact us if you think this is the case.

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[faelau]

I've signed the Icinga CLA.

[bobapple]

@cla-bot check