Problem editing TreeWidget items

[Moezzie]

I have this little program ive been working on for the last week or so and it almost finished but i just cant get the editing function to work.

I have a tree widget with a couple of items in it. When i select one and hit the edit-button a dialog pops up and asks the user to input two new values. When the ok-button is clicked these values are sent to an edit function which is supposed to edit the selected item.
It seems like a really easy job, but somehow it does not work. However it workes just fine in another function so i have no idea whats wrong.

void MainWindowImpl::button_edit_clicked()
{
        // If an item is selected open the dialog
	if(treeWidget->currentItem())
	{
		EditDialog *dialog = new EditDialog;
		dialog->show();
	}
 
        // Edit the selected item
        // This one workes fine. Its just a test though
	if(treeWidget->currentItem())
	{
		item = treeWidget->takeTopLevelItem(treeWidget->indexOfTopLevelItem(treeWidget->currentItem()));
		item->setText(1, "New Date");
		treeWidget->insertTopLevelItem(0, item);
	}
 
	//check
	qDebug() << "Edit clicked";
}
 
// the new values are passed to this funktion
void MainWindowImpl::edit_item(QString col0, QString col1)
{ 
 
// This one does not work, its the same as the same one as above but it produces an error
// When i try to put it inside of a similar if-statementas above, it returns false
// I guess it has something with the selection to do then
	item = treeWidget->takeTopLevelItem(treeWidget->indexOfTopLevelItem(treeWidget->currentItem()));
	item->setText(1, "New Date2");
	treeWidget->insertTopLevelItem(0, item);
 
 
	qDebug() << "Items Recived:" << col0 << col1;
}

void MainWindowImpl::button_edit_clicked()
{
        // If an item is selected open the dialog
	if(treeWidget->currentItem())
	{
		EditDialog *dialog = new EditDialog;
		dialog->show();
	}
	
        // Edit the selected item
        // This one workes fine. Its just a test though
	if(treeWidget->currentItem())
	{
		item = treeWidget->takeTopLevelItem(treeWidget->indexOfTopLevelItem(treeWidget->currentItem()));
		item->setText(1, "New Date");
		treeWidget->insertTopLevelItem(0, item);
	}

	//check
	qDebug() << "Edit clicked";
}

// the new values are passed to this funktion
void MainWindowImpl::edit_item(QString col0, QString col1)
{ 
	
// This one does not work, its the same as the same one as above but it produces an error
// When i try to put it inside of a similar if-statementas above, it returns false
// I guess it has something with the selection to do then
	item = treeWidget->takeTopLevelItem(treeWidget->indexOfTopLevelItem(treeWidget->currentItem()));
	item->setText(1, "New Date2");
	treeWidget->insertTopLevelItem(0, item);

	
	qDebug() << "Items Recived:" << col0 << col1;
}

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This is the debug message i get:

Sending Items: "dsa" and "01.Jan 00"
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1224956224 (LWP 8040)]
0x0804f736 in QTreeWidgetItem::setText (this=0x0, column=1, atext=@0xbf9cadcc) at /usr/include/qt4/QtGui/qtreewidget.h:216
}
, alloc = 0
, size = 0
, data = 0x8058d92, clean = 0
, simpletext = 0
, righttoleft = 0
, asciiCache = 0
, capacity = 0
, reserved = 0
, array = {0
}
}, static shared_empty = {ref = {value = 1
}
, alloc = 0
, size = 0
, data = 0xb774d44e, clean = 0
, simpletext = 0
, righttoleft = 0
, asciiCache = 0
, capacity = 0
, reserved = 0
, array = {0
}
}, d = 0x82db060, static codecForCStrings = 0x0}

Thanks for your time!