Fix panic due to missing swapchain texture. (#141)

* Fix panic due to missing swapchain texture.

* Format.

src/egui_node.rs

@@ -315,6 +315,13 @@ impl Node for EguiNode {
                 return Ok(()); // No window
             };
 
+        let swap_chain_texture =
+            if let Some(swap_chain_texture) = extracted_window.swap_chain_texture.as_ref() {
+                swap_chain_texture
+            } else {
+                return Ok(()); // No swapchain texture
+            };
+
         let render_queue = world.get_resource::<RenderQueue>().unwrap();
 
         let (vertex_buffer, index_buffer) = match (&self.vertex_buffer, &self.index_buffer) {
@@ -329,8 +336,6 @@ impl Node for EguiNode {
 
         let egui_transforms = world.get_resource::<EguiTransforms>().unwrap();
 
-        let swap_chain_texture = extracted_window.swap_chain_texture.as_ref().unwrap();
-
         let mut render_pass =
             render_context
                 .command_encoder