Jérôme Dubois authored Nov 20, 2021 and Alexandre Duret-Lutz committed Nov 22, 2021

* spot/kripke/kripkegraph.hh, spot/misc/hash.hh, spot/twa/taatgba.cc,
  spot/twa/twagraph.hh, tests/core/ngraph.cc: Replace subtraction of
  pointeur minus nullptr by an explicit cast to size_t.
* spot/twa/acc.hh: Add explicit default copy assignment operator for
  rs_pair.