no clean exit if none of the input datasets are valid

Error with file /data/id15/inhouse4/ihma109/id15/ACL9011001b/ACL9011001b_0001/ACL9011001b_0001.h5: Cannot access data 1.1/instrument/pilatus/data in file /data/id15/inhouse4/ihma109/id15/ACL9011001b/ACL9011001b_0001/ACL9011001b_0001.h5 - ignoring this dataset!
Traceback (most recent call last):
  File "/scisoft/tomotools_env/integrator/ubuntu20.04/x86_64/2021.1/bin/integrate-slurm", line 8, in <module>
    sys.exit(integrate_slurm_cli())
  File "/scisoft/tomotools_env/integrator/ubuntu20.04/x86_64/2021.1/lib/python3.8/site-packages/integrator/app/integrate_slurm.py", line 41, in integrate_slurm_cli
    if datasets[0] is None or output_files[0] is None:
IndexError: list index out of range