Fixes in DL1 data check

[moralejo]

Fixed warning message

[codecov]

Codecov Report

Merging #932 (b21ad32) into master (62951c5) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #932      +/-   ##
==========================================
- Coverage   85.52%   85.49%   -0.04%     
==========================================
  Files          78       78              
  Lines        6459     6459              
==========================================
- Hits         5524     5522       -2     
- Misses        935      937       +2     

Impacted Files	Coverage Δ
lstchain/reco/r0_to_dl1.py	93.08% <0.00%> (-0.63%)	⬇️

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