PVS-Studio warning V530 for TPP

static void clearTagNames() {
   std::vector<const char *>ptrs;
   for (tagname_set::iterator i = tagnames.begin();
        i!=tagnames.end();i++) {
      ptrs.push_back(*i);
   }
   for (tagname_set::iterator j = attrnames.begin();
        j!=attrnames.end();j++) {
      ptrs.push_back(*j);
   }
   tagnames.empty();
   attrnames.empty();
   for (size_t n=ptrs.size();n--;) {
      delete [] (char *)(ptrs[n]); // cast away const
   }
}

This suspicious code was found in TPP project by PVS-Studio static code analyzer.
Warning message is:
V530 The return value of function 'empty' is required to be utilized. tag.cxx 72

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/