PVS-Studio warning V503 for Scilab

int write_xml_states(....)
{
  ....
  FILE *fd = NULL;
  ....
  wcfopen(fd, (char*)xmlfile, "wb");
  if (fd < 0)
  {
    sciprint(_("Error: cannot write to  '%s'  \n"), xmlfile);
    ....
}

This suspicious code was found in Scilab project by PVS-Studio static code analyzer.
Warning message is:
V503 This is a nonsensical comparison: pointer < 0. scicos.c 5826

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/