fix issues

app.py

@@ -66,14 +66,6 @@ def create_app():
                         file_types=[".npy"]
                     )
 
-                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)
 
@@ -82,6 +74,14 @@ def create_app():
                         return None
                     return visualize_et_data(traj_file.name, char_file.name)
 
+                with gr.Row():
+                    visualize_btn = gr.Button("Visualize")
+                    visualize_btn.click(
+                        process_et_files,
+                        inputs=[traj_file, char_file],
+                        outputs=[et_viewer]
+                    )
+
     return demo