Update detect.py (Fix save-csv: Ensure header is written to CSV) (#13472)

This commit resolves an issue where the save-csv command did not write the CSV header. The code now correctly saves the header in the CSV file.

Signed-off-by: Ali Ghanbari <alighanbari446@gmail.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

detect.py

@@ -219,9 +219,10 @@ def run(
         def write_to_csv(image_name, prediction, confidence):
             """Writes prediction data for an image to a CSV file, appending if the file exists."""
             data = {"Image Name": image_name, "Prediction": prediction, "Confidence": confidence}
+            file_exists = os.path.isfile(csv_path)
             with open(csv_path, mode="a", newline="") as f:
                 writer = csv.DictWriter(f, fieldnames=data.keys())
-                if not csv_path.is_file():
+                if not file_exists:
                     writer.writeheader()
                 writer.writerow(data)