Avoid an unnecessary panic when the script task deals with a GC after…

… the layout thread is unreachable.

components/script/dom/node.rs

@@ -192,7 +192,9 @@ impl Node {
         debug_assert!(thread_state::get().is_script());
         let win = window_from_node(self);
         self.style_and_layout_data.set(None);
-        win.layout_chan().send(Msg::ReapStyleAndLayoutData(data)).unwrap();
+        if win.layout_chan().send(Msg::ReapStyleAndLayoutData(data)).is_err() {
+            warn!("layout thread unreachable - leaking layout data");
+        }
     }
 
     /// Adds a new child to the end of this node's list of children.