I'm trying to dynamicly add and remove widgets to a gridlayout based on what the user selects in a combobox named EffectChoice. This works perfect if I select an effect with one argument(a new ComboBox is added) and then choose an effect with 0 arguments(the ComboBox is deleted). However, if I then select the effect with one argument again, Qt crashes at this line:
Qt Code: 
  1. if(!ui->grdVisuals->itemAtPosition(row,x)->isEmpty()){
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This is the full code of the combobox:
Qt Code: 
  1. void MainWindow::on_EfectChoice_ValueChanged(QString Effect){
  2.     int row = QObject::sender()->property("Row").toInt(); //get the row number
  3.     for(int x=1;x<ui->grdVisuals->columnCount();x++){ //loop all the row items except the first one
  4.         if(!ui->grdVisuals->itemAtPosition(row,x)->isEmpty()){
  5.             QComboBox* cboVar = qobject_cast<QComboBox*>(ui->grdVisuals->itemAtPosition(row,x)->widget());
  6.             if(cboVar){//remove the widget
  7.                 ui->grdVisuals->removeWidget(cboVar);
  8.                 ui->grdVisuals->removeItem(ui->grdVisuals->itemAtPosition(row,x));
  9.                 cboVar->setParent(NULL);
  10.                 delete cboVar;
  11.             }
  12.         }
  13.     }
  14.     for(int i=0;i < GLOutput->VisualList.count();i++){//loop the Visuals list to retrieve effect data
  15.         if(GLOutput->VisualList.at(i).Visual == Effect){
  16.             for(int a=0; a<GLOutput->VisualList.at(i).ArgCount;a++){//create a new combobox for each argument of the effect
  17.                 QComboBox* InputType =  new QComboBox;
  18.                 InputType->setMinimumWidth(200);
  19.                 ui->grdVisuals->addWidget(InputType,row,a+1,1,1,Qt::AlignLeft);
  20.             }
  21.         }
  22.     }
  23. }
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I'd google it, but I don't really know what's causing it and what searchwords to use.