PVS-Studio warning V575 for ReactOS

VOID WinLdrSetupEms(IN PCHAR BootOptions)
{
  PCHAR RedirectPort;
  ....
  RedirectPort = strstr(RedirectPort, "com");
  if (RedirectPort)
  {
    ....
  }
  else
  {
    RedirectPort = strstr(RedirectPort, "usebiossettings");
  ....
}

This suspicious code was found in ReactOS project by PVS-Studio static code analyzer.
Warning message is:
V575 The null pointer is passed into 'strstr' function. Inspect the first argument. headless.c 263

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/