using "none" for no refiner selection

app.py

@@ -147,7 +147,7 @@ def run_inference(config, config_history, progress=gr.Progress(track_tqdm=True))
             torch_dtype = get_data_type(config["data_type"]), 
             variant = get_variant(config["variant"])).to(config["device"])
         
-        if config['refiner'] != '':
+        if config['refiner'].lower() != 'none':
             refiner = DiffusionPipeline.from_pretrained(
                     config['refiner'],
                     text_encoder_2=pipeline.text_encoder_2,