Pen tool: do not merge with ancestor layer as it breaks the graph (#3347)

Author: 0HyperCube

editor/src/messages/tool/common_functionality/graph_modification_utils.rs

@@ -32,7 +32,8 @@ pub fn find_spline(document: &DocumentMessageHandler, layer: LayerNodeIdentifier
 
 /// Merge `second_layer` to the `first_layer`.
 pub fn merge_layers(document: &DocumentMessageHandler, first_layer: LayerNodeIdentifier, second_layer: LayerNodeIdentifier, responses: &mut VecDeque<Message>) {
-if first_layer == second_layer {
+// Skip layers that are children of each other (or the same)
+if first_layer.ancestors(document.metadata()).any(|l| l == second_layer) || second_layer.ancestors(document.metadata()).any(|l| l == first_layer) {
 return;
 }
 // Calculate the downstream transforms in order to bring the other vector geometry into the same layer space