fix: blob were saved directly at shard folder instead of sub folder ``blobs`` if no custom blob path was set

Maybe something like this?

BREAKING IF UPGRADING FROM 0.42:
    - The sub-folder in which blobs are saved has accidentily been changed with 0.42, this change is now being reverted. 
   For users upgrading from 0.42 this means that they have to move the files from <blob_path>... to ...
   Users who upgrade from a version priour to 0.42 can upgrade without worries.