Provide fallback translations for imprint feedbacks

[membralala]

Short description

This PR should fix the feedback view error, that was shown, when imprint feedback was submitted in a language, that does not exist for this regions feedback.

Proposed changes

• Use fallback translation for the title of an imprint feedback, if the language exists in this region
• Use default backend language, otherwise

Resolved issues

Fixes: #1717

There was a previous PR, where I used a different solution which did not work out. When I dropped the changes, the PR was closed automatically. However, for full discussion also see #1730.

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Pull Request Review Guidelines

[codeclimate[bot]]

Code Climate has analyzed commit 4f419e82 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 25.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 74.2% (0.0% change).

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