* Fix example hello_world_par

* Added warning for glow eframe when creating `Context::create_viewport_sync` in other thread, or cannot be rendered!
* Fix clippy warning

examples/hello_world_par/src/main.rs

@@ -136,9 +136,6 @@ impl eframe::App for MyApp {
 
         for (_handle, show_tx) in &self.threads {
             let _ = show_tx.send(ctx.clone());
-        }
-
-        for _ in 0..self.threads.len() {
             let _ = self.on_done_rc.recv();
         }
     }