diff -r 60145497de34 src/gui/qgsmapcanvas.cpp
--- a/src/gui/qgsmapcanvas.cpp	Sat Mar 06 13:49:55 2010 +0000
+++ b/src/gui/qgsmapcanvas.cpp	Thu Mar 11 13:35:31 2010 +0100
@@ -236,6 +236,10 @@
   for ( i = 0; i < layers.size(); i++ )
   {
     QgsMapCanvasLayer& lyr = layers[i];
+    if( lyr.layer() == NULL)
+    {
+      continue;
+    }
     if ( lyr.isVisible() )
     {
       layerSet.push_back( lyr.layer()->getLayerID() );