segment fault when using MySQL in qt

I was using MySQL in qt and try to use "select" sentence. When the query was destructing, it told me a segment fault appeared in the 431th line of  \src\plugins\sqldrivers\mysql\qsql_mysql.cpp. To solve it, i changed 

if(qIsTimeOrDate(field.myField->type)) {
      reinterpret_cast<MYSQL_TIME*>(field.outField)->~MYSQL_TIME();
}

to

if(field.myField != 0) 
{
     if(qIsTimeOrDate(field.myField->type)) 
     {  
          reinterpret_cast<MYSQL_TIME*>(field.outField)->~MYSQL_TIME(); 
     } 
}

and compile the .dll file. And the problem was solved.