Issue when output dir not defined or .nxtomo provided without any path

  File "/mnt/multipath-shares/scisoft/tomotools_env/tomwer/ubuntu20_x86_64/2022-11-16/bin/nabu", line 8, in <module>
    sys.exit(main())
  File "/mnt/multipath-shares/scisoft/tomotools_env/tomwer/ubuntu20_x86_64/2022-11-16/lib/python3.8/site-packages/nabu/app/reconstruct.py", line 111, in main
    R.merge_hdf5_reconstructions()
  File "/mnt/multipath-shares/scisoft/tomotools_env/tomwer/ubuntu20_x86_64/2022-11-16/lib/python3.8/site-packages/nabu/pipeline/fullfield/reconstruction.py", line 647, in merge_hdf5_reconstructions
    merge_hdf5_files(
  File "/mnt/multipath-shares/scisoft/tomotools_env/tomwer/ubuntu20_x86_64/2022-11-16/lib/python3.8/site-packages/nabu/io/writer.py", line 436, in merge_hdf5_files
    virtual_layout = create_virtual_layout(files_or_pattern, h5_path, base_dir=base_dir, axis=axis)
  File "/mnt/multipath-shares/scisoft/tomotools_env/tomwer/ubuntu20_x86_64/2022-11-16/lib/python3.8/site-packages/nabu/io/writer.py", line 352, in create_virtual_layout
    chdir(base_dir)
FileNotFoundError: [Errno 2] No such file or directory: ''