fix indexing issue in sd reference pipeline (#4531)

examples/community/stable_diffusion_reference.py

@@ -153,8 +153,6 @@ class StableDiffusionReferencePipeline(StableDiffusionPipeline):
                 )
             ref_image_latents = ref_image_latents.repeat(batch_size // ref_image_latents.shape[0], 1, 1, 1)
 
-        ref_image_latents = torch.cat([ref_image_latents] * 2) if do_classifier_free_guidance else ref_image_latents
-
         # aligning device to prevent device errors when concating it with the latent model input
         ref_image_latents = ref_image_latents.to(device=device, dtype=dtype)
         return ref_image_latents
@@ -733,6 +731,7 @@ class StableDiffusionReferencePipeline(StableDiffusionPipeline):
                         1,
                     ),
                 )
+                ref_xt = torch.cat([ref_xt] * 2) if do_classifier_free_guidance else ref_xt
                 ref_xt = self.scheduler.scale_model_input(ref_xt, t)
 
                 MODE = "write"