Update app.py

app.py

@@ -170,7 +170,7 @@ You should use {formatted_words} to trigger the image generation.
         escaped_prompt = prompt.replace("'", "''")
         widget_content += f"""- text: '{escaped_prompt if escaped_prompt else ' ' }'
   parameters:
-      negative_prompt: {negative_prompt}
+      negative_prompt: '{negative_prompt}'
   output:
     url: >-
       {image}