Update pipeline_animatediff_video2video.py (huggingface#7457)

* Update pipeline_animatediff_video2video.py

* commit with test for whether latent input can be passed into animatediffvid2vid

src/diffusers/pipelines/animatediff/pipeline_animatediff_video2video.py

@@ -638,7 +638,7 @@ def prepare_latents(
         # video must be a list of list of images
         # the outer list denotes having multiple videos as input, whereas inner list means the frames of the video
         # as a list of images
-        if not isinstance(video[0], list):
+        if video and not isinstance(video[0], list):
             video = [video]
         if latents is None:
             video = torch.cat(

tests/pipelines/animatediff/test_animatediff_video2video.py

@@ -269,6 +269,17 @@ def test_prompt_embeds(self):
         inputs["prompt_embeds"] = torch.randn((1, 4, 32), device=torch_device)
         pipe(**inputs)
 
+    def test_latent_inputs(self):
+        components = self.get_dummy_components()
+        pipe = self.pipeline_class(**components)
+        pipe.set_progress_bar_config(disable=None)
+        pipe.to(torch_device)
+
+        inputs = self.get_dummy_inputs(torch_device)
+        inputs["latents"] = torch.randn((1, 4, 1, 32, 32), device=torch_device)
+        inputs.pop("video")
+        pipe(**inputs)
+
     @unittest.skipIf(
         torch_device != "cuda" or not is_xformers_available(),
         reason="XFormers attention is only available with CUDA and `xformers` installed",