PVS-Studio warning V502 for Sanitiser for OpenType

bool version_2;

bool ots_gdef_parse(....)
{
  ...
  const unsigned gdef_header_end = static_cast<unsigned>(8) +
    gdef->version_2 ? static_cast<unsigned>(2) :
                      static_cast<unsigned>(0);
  ...
}

This suspicious code was found in Sanitiser for OpenType project by PVS-Studio static code analyzer.
Warning message is:
V502 Perhaps the '?:' operator works in a different way than it was expected. The '?:' operator has a lower priority than the '+' operator. ots gdef.cc 278

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/