https://github.com/bitcoin/bitcoin/blob/9ad6f14175c19b5d47267c3dd5840c14bad43c83/src/validation.cpp#L3711

If i'm following right the flow of the code, when we hit this lane `pindex` should be always equal to nullptr thus this check may be omitted
{
    uiInterface.NotifyAlertChanged();
#if HAVE_SYSTEM
    std::string strCmd = gArgs.GetArg("-alertnotify", "");
    if (strCmd.empty()) return;
    
    
    
    std::string singleQuote("'");
    std::string safeStatus = SanitizeString(strMessage);
    safeStatus = singleQuote+safeStatus+singleQuote;
    boost::replace_all(strCmd, "%s", safeStatus);
    std::thread t(runCommand, strCmd);
    t.detach(); 
#endif
}
static void CheckForkWarningConditions() EXCLUSIVE_LOCKS_REQUIRED(cs_main)