fix some small issues

app.py

@@ -66,21 +66,24 @@ def create_app():
                         file_types=[".npy"]
                     )
 
-                def process_et_files(traj_file, char_file):
-                    if traj_file is None or char_file is None:
-                        return None
-                    return visualize_et_data(traj_file.name, char_file.name)
+                et_viewer = Rerun(streaming=False)
 
                 with gr.Row():
                     visualize_btn = gr.Button("Visualize")
-                    visualize_btn.click(
-                        process_et_files,
-                        inputs=[traj_file, char_file],
-                        outputs=[et_viewer]
-                    )
 
                 with gr.Row():
-                    et_viewer = Rerun(streaming=False)
+                    et_viewer.render()
+
+                def process_et_files(traj_file, char_file):
+                    if traj_file is None or char_file is None:
+                        return None
+                    return visualize_et_data(traj_file.name, char_file.name)
+
+                visualize_btn.click(
+                    process_et_files,
+                    inputs=[traj_file, char_file],
+                    outputs=[et_viewer]
+                )
 
     return demo