ENA search in UI expects sample accession SAMN.* to exist

[pansapiens]

There are cases where a run exists, but the sample accession is not available on ENA eg SRR26449549 and sample SAMN37904062.

This causes an exception when the backend attempts retrieve sample metadata, preventing these FASTQs from being added to the cart.

File "/app/laxy_backend/views.py", line 530, in get
   ena_result = ena.get_organism_from_sample_accession(accession)
 File "/usr/local/lib/python3.6/site-packages/cache_memoize/__init__.py", line 118, in inner
  result = func(*args, **kwargs)
 File "/app/laxy_backend/ena.py", line 401, in get_organism_from_sample_accession
   resp.raise_for_status()
  File "/usr/local/lib/python3.6/site-packages/requests/models.py", line 940, in raise_for_status
   raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 404 Client Error:  for url: https://www.ebi.ac.uk/ena/browser/api/xml/SAMN44459348