transforms: Fix -Wtype-limits warning
transforms: Fix -Wtype-limits warning

Fixes:
MakeNondet.cpp:239:16: warning: comparison of unsigned expression in ‘>= 0’ is always true [-Wtype-limits]
  239 |     while (end >= 0 && std::isspace(str[end]))
      |            ~~~~^~~~
MakeNondet.cpp: In function ‘std::string lastWord(const  string&)’:
MakeNondet.cpp:249:16: warning: comparison of unsigned expression in ‘>= 0’ is always true [-Wtype-limits]
  249 |     while (end >= 0 && std::isspace(str[end]))
      |            ~~~~^~~~
MakeNondet.cpp:252:16: warning: comparison of unsigned expression in ‘>= 0’ is always true [-Wtype-limits]
  252 |     while (end >= 0 && !std::isspace(str[end])) {
      |            ~~~~^~~~

staticafi/symbiotic,staticafi/symbiotic,staticafi/symbiotic,staticafi/symbiotic