QStringList, QList<QString> Iterator abnormal behavior

Following code works for some values of i (i is the quantity of string object inserted into the list) whilst does not work for others. When it does not work this error is shown:

ASSERT failure in QList::insert: "The specified iterator argument 'before' is invalid", file  C:/Qt/6.8.1/llvm-mingw_64/include/QtCore/qlist.h, line 505 qtc.process_stub: Inferior: QProcess::Crashed "Process crashed".

#include <QCoreApplication>
#include <QString>
#include <QList>
#include <QTextStream>
#include <QStringList>

int main(int argc, char *argv[])
{
   QCoreApplication a(argc, argv);

   QList<QString> list_string;
   QList<QString>::iterator list_it;

   //QStringList list_string;
   //QStringList::iterator list_it;

   QTextStream out(stdout);

 

   //functions with element number 1, 5, 6, 15, 16, ...
   //does not function with element number 2, 4, 6, 7, 8, 9, ...

   for(int i = 0; i < 5; i++)
   

{       list_string.append("one");    }

   list_it = list_string.begin();
   while(list_it != list_string.end())
   {
      list_it++;
      if(list_it != list_string.end())
     

{          list_string.insert(list_it, " and ");          list_it++;       }

   }

   list_it = list_string.begin();
   while(list_it != list_string.end())
   

{       out << *list_it << Qt::endl;       list_it++;    }

   return a.exec();
}