2754 partial instead of error (#2900)
* add a test
* ensure preview/viewer/partial are always returned
* set num_rows=None if we can't get the value
* fix type
* fix types
* fix type
* Update services/worker/src/worker/dtos.py
Co-authored-by: Quentin Lhoest <42851186+lhoestq@users.noreply.github.com>
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Co-authored-by: Quentin Lhoest <42851186+lhoestq@users.noreply.github.com>
