[Java-gnome-developer] Strange error mesage when using treeView

[Kyrre N. S. <ky...@so...>]

I just wrote up some code to present the channellist in givtv, following
the treeView tutor quite closely. But when i try to run it, i get this
backtrace, and i don't know what it means:

*********** START BACKTRACE ******************

java.lang.Exception: gtk_tree_view_column_cell_layout_add_attribute:
assertion `info != NULL' failed
   at org.gnu.glib.GObject.printStackTrace(GObject.java:675)
   at
org.gnu.gtk.TreeViewColumn.addAttributeMapping(TreeViewColumn.java:387)
   at
net.sourceforge.givtv.gnomeFrontend.MainWindow.setupTreeView(MainWindow.java:143)
   at
net.sourceforge.givtv.gnomeFrontend.MainWindow.createView(MainWindow.java:63)
   at
net.sourceforge.givtv.gnomeFrontend.MainWindow.<init>(MainWindow.java:35)
   at net.sourceforge.givtv.gnomeFrontend.Givtv.<init>(Givtv.java:41)
   at net.sourceforge.givtv.gnomeFrontend.Givtv.main(Givtv.java:57)
Exception in thread "main" java.lang.NullPointerException
   at
net.sourceforge.givtv.gnomeFrontend.MainWindow.populateChannels(MainWindow.java:121)
   at
net.sourceforge.givtv.gnomeFrontend.MainWindow.<init>(MainWindow.java:36)
   at net.sourceforge.givtv.gnomeFrontend.Givtv.<init>(Givtv.java:41)
   at net.sourceforge.givtv.gnomeFrontend.Givtv.main(Givtv.java:57)

*********** END BACKTRACE ******************

This is the offending part of MainWindow.java:
	private void setupTreeView () {
		//Setup the backend storage
		//DataColumn[] columns = new DataColumnString[1];
		datacolumn0 = new DataColumnString ();
		channellist = new ListStore(new DataColumn[] {datacolumn0});
		channellistWidget.setModel(channellist);
		
		//Setup the visual appearance of the treeView
		TreeViewColumn col0 = new TreeViewColumn ();
			CellRendererText render0 = new CellRendererText ();
			col0.setTitle("Channel name");
			col0.addAttributeMapping(render0, CellRendererText.Attribute.TEXT,
datacolumn0);
		
----****---->	channellistWidget.appendColumn(col0); <---- Line 143
		
		//General setup of the widget
		channellistWidget.setEnableSearch(true);
		channellistWidget.setAlternateRowColor(true);
		channellistWidget.setHeadersVisible(false);
		
	}

What does it mean? I don't understand... Just say so if you need more
code! Its all GPL, so it isn't any problem :)