added edge case where model has no config

app.py

@@ -131,6 +131,9 @@ def button_click(hf_model_id, conv_template, quantization, oauth_token: gr.OAuth
     if type(model_info) != huggingface_hub.hf_api.ModelInfo:
         os.system("rm -rf dist/")
         return "Entered Huggingface model ID is not a model repository"
+    if "model_type" not in model_info.config:
+        os.system("rm -rf dist/")
+        return "Cannot infer model type from config file"
     if model_info.config['model_type'] not in SUPPORTED_MODEL_TYPES:
         os.system("rm -rf dist/")
         return f"Model type ({model_info.config['model_type']}) currently not supported by MLC-LLM"