Initialize seeds to prevent crashing.

If the user selects one of the (empty) image cells on startup, then runs
a query, the seed would be empty before this change, and the app
crashed.

Ideally, we should disable the radio buttons until they have some
content, but I'm lazy right now.

app.py

@@ -12,7 +12,7 @@ SELECT_LABEL = "Select as seed"
 with gr.Blocks(css=".container { max-width: 800px; margin: auto; }") as demo:
     state = gr.Variable({
         'selected': -1,
-        'seeds': []
+        'seeds': [random.randint(0, 2 ** 32 - 1) for _ in range(6)]
     })
 
     def infer_seeded_image(prompt, seed):