fix issue

app.py

@@ -66,6 +66,11 @@ 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)
+
                 with gr.Row():
                     visualize_btn = gr.Button("Visualize")
                     visualize_btn.click(
@@ -77,11 +82,6 @@ def create_app():
                 with gr.Row():
                     et_viewer = Rerun(streaming=False)
 
-                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)
-
     return demo