[librender] fix crash when rendering with an empty node graph

src/libRender/RadiumNBR/NodeBasedRenderer.cpp

@@ -281,7 +281,7 @@ void NodeBasedRenderer::uiInternal( const ViewingParameters& renderData ) {
 }
 
 void NodeBasedRenderer::postProcessInternal( const ViewingParameters& /* renderData */ ) {
-    if ( true /*m_colorTexture*/ )
+    if ( m_colorTexture )
     {
         m_postprocessFbo->bind();