Handle exceptions by reference

[pmaciel]

This is good practice. Related to PR
ecmwf/eckit#179

[FussyDuck]

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.18%. Comparing base (d025fb1) to head (5b445e9).

Files with missing lines	Patch %	Lines
src/odc/odccapi.cc	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #34      +/-   ##
===========================================
- Coverage    87.18%   87.18%   -0.01%     
===========================================
  Files          189      188       -1     
  Lines        15043    15041       -2     
  Branches      1352     1352              
===========================================
- Hits         13115    13113       -2     
  Misses        1928     1928              

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