fix app

app.py

@@ -257,7 +257,7 @@ with gr.Blocks(css=css) as demo:
         )
 
         prompt_in = gr.Textbox(label="Prompt", placeholder="A chihuahua in astronaut suit floating in space, cinematic lighting, glow effect")
-        output_size = gr.Dropdown(["576x1024", "256x256"], value="256x256", label="Output Size", info="576x1024 is watermark-free"),
+        output_size = gr.Dropdown(["576x1024", "256x256"], value=["256x256"], label="Output Size", info="576x1024 is watermark-free"),
         submit_btn = gr.Button("Generate")
         video_result = gr.Video(label="Video Output")