Mask gets lost in `prepare_data`?

It looks like numpy.copy does not preserve masking. We use it here: https://git.ufz.de/FINAM/finam/-/blob/main/src/finam/data/tools.py#L80

Check that masking is preserved!

added bug data labels

Confirmed, mask is lost in the function call.

mentioned in merge request !270 (merged)

changed the description

mentioned in commit 659e6f24

closed with merge request !270 (merged)