Fix bug in opt_R2num() when reading X,Y,Z tile name (bad variable name)

[joa-quim]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.77%. Comparing base (0fa3f8d) to head (a98ffce).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/common_options.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1698      +/-   ##
==========================================
+ Coverage   85.75%   85.77%   +0.02%     
==========================================
  Files         164      164              
  Lines       22937    22937              
==========================================
+ Hits        19669    19675       +6     
+ Misses       3268     3262       -6     

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