Fix bug with WanAnimateToVideo node. (Comfy-Org#9988)

Author: comfyanonymous

comfy_extras/nodes_wan.py

@@ -1210,7 +1210,7 @@ def execute(cls, positive, negative, vae, width, height, length, batch_size, con
                 background_video = background_video[video_frame_offset:]
                 background_video = comfy.utils.common_upscale(background_video[:length].movedim(-1, 1), width, height, "area", "center").movedim(1, -1)
                 if background_video.shape[0] > ref_images_num:
-                    image[ref_images_num:background_video.shape[0] - ref_images_num] = background_video[ref_images_num:]
+                    image[ref_images_num:background_video.shape[0]] = background_video[ref_images_num:]
 
         mask_refmotion = torch.ones((1, 1, latent_length * 4, concat_latent_image.shape[-2], concat_latent_image.shape[-1]), device=mask.device, dtype=mask.dtype)
         if continue_motion is not None: