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/render/backend/audiorenderbackend.cpp

@@ -34,6 +34,9 @@ void AudioRenderBackend::InvalidateCache(const rational &start_range, const rati
   // Remove any overlaps so we don't render the same thing twice
   ValidateRanges();
 
+  // Queue value update
+  QueueValueUpdate(TimeRange(start_range, end_range));
+
   // Start caching cycle if it hasn't started already
   CacheNext();
 }