[solved]segfault: QTableWidgetItem->setText

[marinamarina]

I've read that segfaults are usually caused by trying to use inaccessible memory. So, if I'm getting a segfault from trying to manipulate a table widget item, it's probably because the item I'm trying to access doesn't exist.

I'm using a qtablewidget with one row to simulate a Turing machine's input tape.
@
void MainWindow::goForth()
{

//code that isn't part of the problem
//I fetch the widget's current cell to get the symbol that's in it

        move=shifts.indexOf(triplet.at(2)) - 1;   //this decideswether I'll move on the "tape" left, right, or not at all.
        index=ui->tableWidget_2->currentIndex();
        tapeCell=index.column();   
        tapeCell+=move;      //this helps me get the index of the next cell I should move to

        if(tapeCell >  ui->tableWidget_2->columnCount())  //this is the problematic one
        {
            ui->tableWidget_2->insertColumn(ui->tableWidget_2->columnCount()-1);
            QTableWidgetItem *item = new QTableWidgetItem();
            item->setTextAlignment(Qt::AlignCenter);
            QFont *font = new QFont();
            font->setPointSize(30);         //if I should move to a cell that's beyond the right edge of the tape, 
            item->setFont(*font);             //I oughtta create more tape, and that's what I'm trying to do here. 
            item->setText(triplet.at(1));    //insert a column, put a new item there and set it.
            ui->tableWidget_2->setItem(0, tapeCell, item);
            ui->tableWidget_2->setCurrentCell(0, tapeCell);
        }else
            if(tapeCell<0)
            {
                ui->tableWidget_2->insertColumn(0);
                QTableWidgetItem *item = new QTableWidgetItem();
                item->setTextAlignment(Qt::AlignCenter);
                QFont *font = new QFont();
                font->setPointSize(30);                              //now, with this, I don't have a problem. It's exactly the
                item->setFont(*font);                                //same as the problem code, except here I'm setting the 
                item->setText(triplet.at(1));                    // cell using 0, not an int variable.
                ui->tableWidget_2->setItem(0, 0, item);
                ui->tableWidget_2->item(0, 0)->setText(triplet.at(1));
                ui->tableWidget_2->setCurrentCell(0,0);
            }else
            {
        ui->tableWidget_2->item(0, tapeCell)->setText(triplet.at(1));  //when it throws the segfault, this line is 
        ui->tableWidget_2->setCurrentCell(0, tapeCell);    //where it points me to, even though this line shouldn't 

} //be executed because tapeCell is greater than columncount

        stepCount++;
        quintuplet=QString("%1. takt: %2, %3 --> %4").arg(stepCount).arg(cState).arg(cSymbol).arg(triplet.join(", "));
        ui->listWidget->addItem(quintuplet);
    }
}

}
@

I checked the brackets, they're all fine, the if clause is how it should be, I'm setting items left and right... what's wrong?

EDIT: nevermind, figured it out after a nap XD I messed up the setting of the current index that occurs whenever I'm near the edge of the tape.