fix error message when user not logged in

app.py

@@ -115,7 +115,7 @@ def split_upload_model(model_path: str, outdir: str, repo_id: str, oauth_token:
     print("Sharded model has been uploaded successfully!")
 
 def process_model(model_id, q_method, use_imatrix, imatrix_q_method, private_repo, train_data_file, split_model, split_max_tensors, split_max_size, oauth_token: gr.OAuthToken | None):
-    if oauth_token.token is None:
+    if oauth_token is None or oauth_token.token is None:
         raise ValueError("You must be logged in to use GGUF-my-repo")
     model_name = model_id.split('/')[-1]