clean up

[tzaeschke]

Another cleanup for #98 (and #99).

[codecov-commenter]

Codecov Report

Merging #101 (f53dba1) into main (420359e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #101   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files          25       25           
  Lines        1992     1992           
=======================================
  Hits         1960     1960           
  Misses         32       32           

Impacted Files	Coverage Δ
include/phtree/common/b_plus_tree_map.h	98.97% <100.00%> (ø)
include/phtree/common/flat_array_map.h	99.03% <100.00%> (ø)
include/phtree/common/flat_sparse_map.h	97.91% <100.00%> (ø)
include/phtree/v16/node.h	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.