Merging failure does not make job fail

[vuillaut]

@vuillaut It seems other base productions have the same issue:
20221215_v0.9.12_base_prod and 20230127_v0.9.12_base_prod_az_tel

Originally posted by @SeiyaNozaki in #371 (comment)

See e.g.
/fefs/aswg/data/mc/DL1/AllSky/20221215_v0.9.12_base_prod/TrainingDataset/dec_931/Protons/merging-output.e

Traceback (most recent call last):
  File "/fefs/aswg/software/conda/envs/lstchain-v0.9.12/bin/lstchain_merge_hdf5_files", line 8, in <module>
    sys.exit(main())
  File "/fefs/aswg/software/conda/envs/lstchain-v0.9.12/lib/python3.8/site-packages/lstchain/scripts/lstchain_merge_hdf5_files.py", line 88, in main
    auto_merge_h5files(
  File "/fefs/aswg/software/conda/envs/lstchain-v0.9.12/lib/python3.8/site-packages/lstchain/io/io.py", line 341, in auto_merge_h5files
    out_node.append(in_node.read().astype(out_node.dtype))
ValueError: structures must have the same size