diff --git a/qad_blockview/blockview.cpp b/qad_blockview/blockview.cpp
index 583469e..ee7e019 100644
--- a/qad_blockview/blockview.cpp
+++ b/qad_blockview/blockview.cpp
@@ -803,6 +803,7 @@ BlockBusItem * BlockView::connectionBus(BlockItem * b0, BlockItem * b1) const {
 
 
 QList<BlockBusItem * > BlockView::connectionBuses(BlockItem * b0, BlockItem * b1) const {
+	if (!b0 || !b1) return QList<BlockBusItem * >();
 	QSet<BlockBusItem * > bs0 = b0->connectedBuses().toSet(), bs1 = b1->connectedBuses().toSet();
 	return (bs0 & bs1).values();
 }