Fix seed

Currently the seed is ignored, as it is supplied as an unknown parameter (`seed`). Instead, it should be supplied as a generator.

app.py

@@ -42,12 +42,15 @@ def predict(input_image, prompt, negative_prompt, steps, num_samples, scale, see
     init_image = input_image.convert("RGB")
     image = pad_image(init_image)  # resize to integer multiple of 32
     image = image.resize((512, 512))
+    generator = None
+    if seed is not None:
+        generator = torch.Generator(device=device).manual_seed(seed)
     result = dept2img(
         image=image,
         prompt=prompt,
         negative_prompt=negative_prompt,
         depth_image=depth,
-        seed=seed,
+        generator=generator,
         strength=strength,
         num_inference_steps=steps,
         guidance_scale=scale,