copy values whenever the cache is invalidated

Since we're now working with a separate proxy copy of the original node graph,
if the user changes a parameter in one of those nodes (triggering an
InvalidateCache signal), the values in our copied graph need to be updated
with these new values too.

app/widget/timelinewidget/undo/undo.cpp

@@ -22,7 +22,6 @@
 
 #include "node/graph.h"
 
-#include <QDebug>
 Block* CreateSplitBlock(Block* block, rational point, QObject* parent = nullptr)
 {
   Block* copy = static_cast<Block*>(block->copy());