UI: sinfex.cc: work around bison & flex disagreeing on nullptr vs 0 for YY_NULL
UI: sinfex.cc: work around bison & flex disagreeing on nullptr vs 0 for YY_NULL

tim-janik/rapicorn,tim-janik/rapicorn,tim-janik/rapicorn,tim-janik/rapicorn,tim-janik/rapicorn