handled error with file

app.py

@@ -644,11 +644,14 @@ elif app_mode =='Run on Test Videos':
 
             # st.text('Video Processed')
             with view.container():
-                writer.close()
-                # out. release()
-                output_video = open(output_file,'rb')
-                out_bytes = output_video.read()
-                st.video(out_bytes)
+                if writer is not None:  # ✅ safeguard
+                    writer.close()
+                    output_video = open(output_file,'rb')
+                    out_bytes = output_video.read()
+                    st.video(out_bytes)
+                    print(f'Output file - {output_file}')
+                else:
+                    st.warning("No video was processed, writer is empty.")
                 # out.release()
                 
                 print(f'Output file - {output_file}')