Fixes bug

• also fixes the input field for nullable boolean values
• Frontend test fails because of framework problems

Closes #291

added Bug priority::3 scope::Backend + 1 deleted label

assigned to @mweise

approved this merge request

added 5 commits

• 6ecf4bbd...38382b40 - 4 commits from branch dev
• 13b85fc6 - Merge branch 'dev' into 291-modify-primary-keys-not-possible

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added 1 commit

• 6f0d381d - Not testable

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mentioned in commit 9f7293f1

merged