Remove zarr-errors handling from tasks

[tcompa]

There are few places where we use try/except for zarr errors, which could be handled better (i.e. the try/except should be replaced by an if/else, with conditions based on zarr attributes).

1. In create-omer-zarr-multiplex, when looping over wells
2. In apply_registration_to_image, when getting the current label_list.

Note that this is not applicable (for the moment) to the ContainsArrayError errors in yokogawa-to-zarr and MIP tasks.

[tcompa]

Related: #621