fix IndexError on xarray 2022.6.0

[avaldebe]

close #710

[codecov]

Codecov Report

Merging #711 (67109d1) into main-dev (bee5311) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           main-dev     #711      +/-   ##
============================================
- Coverage     77.38%   77.37%   -0.01%     
============================================
  Files            97       97              
  Lines         17556    17559       +3     
============================================
+ Hits          13585    13587       +2     
- Misses         3971     3972       +1     

Flag	Coverage Δ
unittests	77.37% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pyaerocom/aeroval/coldatatojson_helpers.py	68.65% <100.00%> (+0.05%)	⬆️
pyaerocom/config.py	83.56% <0.00%> (-0.17%)	⬇️
pyaerocom/io/read_eea_aqerep_base.py	84.70% <0.00%> (+0.04%)	⬆️

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[lewisblake]

Looks good to merge. Thanks for taking care of this!

[lewisblake]

🥇