Fix creation of session dir.

app.py

@@ -164,6 +164,7 @@ def generate_and_extract_glb(
         str: The path to the extracted GLB file (for download).
     """
     user_dir = os.path.join(TMP_DIR, str(req.session_hash))
+    os.makedirs(user_dir, exist_ok=True)  # Ensure directory exists
 
     # Generate 3D model
     if not is_multiimage:
@@ -240,6 +241,7 @@ def extract_gaussian(state: dict, req: gr.Request) -> Tuple[str, str]:
         Tuple[str, str]: Paths to the extracted Gaussian file (for display and download)
     """
     user_dir = os.path.join(TMP_DIR, str(req.session_hash))
+    os.makedirs(user_dir, exist_ok=True)  # Ensure directory exists
     gs, _ = unpack_state(state)
     gaussian_path = os.path.join(user_dir, "sample.ply")
     gs.save_ply(gaussian_path)