Update app.py

app.py

@@ -520,11 +520,6 @@ def step1_extract(
     ret = proc.wait()
 
     frames = sorted(raw_dir.glob(f"{prefix}_*.{out_format}"), key=_natural_key)
-        try:
-            err = proc.stderr.read() if proc.stderr else ""
-        except Exception:
-            err = ""
-        return None, None, f"FFmpeg error or no frames produced.\\n\\n{err}", cmd_preview, last_html, None, None, None
 
     gallery = sample_paths(frames, 30)
     zip_path = work / "frames.zip"