Im became fool with QTableWidgetItem

[zorro68]

My project works fine, and now (and i dont know why) have and error. Im trying to read from a tablewidget and write to a file, and I use this functions:

QString Sheet::getcellvalue(int row,int col)
{
	QTableWidgetItem *newItem = tabla->item(row,col);
	QString qv = newItem->text();
	return qv;
}

QString Sheet::getcellvalue(int row,int col)
{
	QTableWidgetItem *newItem = tabla->item(row,col);
	QString qv = newItem->text();
	return qv;
}

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where "tabla" is a QTableWidget. Now the compiler says:

Excepción no controlada en 0x6524c1ac en QTDAM.exe: 0xC0000005: Infracción de acceso al leer la ubicación 0x00000000.

I was using .toStdString to convert QStrings to strings, and now .toLatin1. And when i change this, this code give me this error ????????.

Why? and How to programm well.

Please help.
Thanks