LiveScene: Fix bug/crash when we have an empty LiveScene ( no input connection )

Author: lucienfostier

src/IECoreNuke/LiveScene.cpp

@@ -347,6 +347,7 @@ void LiveScene::path( Path &p ) const
 Imath::Box3d LiveScene::readBound( double time ) const
 {
 	Imath::Box3d bound;
+	bound.makeEmpty();
 	IECoreScene::SceneInterface::Path rootPath, currentPath;
 	for( unsigned i=0; i < objects( &time ); ++i )
 	{

test/IECoreNuke/LiveSceneKnobTest.py

@@ -50,6 +50,17 @@ def testNameAndLabel( self ) :
 		self.assertEqual( k.name(), "scene" )
 		self.assertEqual( k.label(), "Scene" )
 
+	def testEmptyScene( self ) :
+		import imath
+
+		n = nuke.createNode( "ieLiveScene" )
+		liveScene = n.knob( "scene" ).getValue()
+
+		self.assertEqual( liveScene.childNames(), [] )
+		self.assertEqual( liveScene.readTransform( 0 ).value.transform, imath.M44d() )
+		self.assertEqual( liveScene.readBound( 0 ), imath.Box3d() )
+		self.assertTrue( isinstance( liveScene.readObject( 0 ), IECore.NullObject ) )
+
 	def testAccessors( self ) :
 
 		n = nuke.createNode( "ieLiveScene" )