Segmentation Fault

[mistergug]

I execute my serv in linux. Erro in gdb:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb64beb70 (LWP 1063)]
0x080aa456 in MySQLResult::getDataString(std::string const&) ()

I modified the file "databasemysql.cpp" but the error continued

BEFORE:

std::string MySQLResult::getDataString(const std::string& s)
{
listNames_t::iterator it = m_listNames.find(s);
if(it != m_listNames.end())
return m_row[it->second] ? std::string(m_row[it->second]) : std::string();
std::clog << "Error during getDataString(" << s << ")." << std::endl;
return std::string(); // Failed
}

AFTER:

std::string MySQLResult::getDataString(const std::string &s)
{
listNames_t::iterator it = m_listNames.find(s);
if(it != m_listNames.end() ){
  if(m_row[it->second] == NULL)
   return std::string("");
  else
   return std::string(m_row[it->second]);
}
std::cout << "Error during getDataString(" << s << ")." << std::endl;
return std::string(""); // Failed
}

the error continues...

Thank you