fix huggingface#3487 initial latents are now only scaled by init_noise_sigma when pure noise

updated this commit w.r.t the latest merge here: huggingface#3533

Author: rupert

src/diffusers/pipelines/stable_diffusion/pipeline_stable_diffusion_inpaint.py

@@ -648,13 +648,13 @@ def prepare_latents(
 
         if latents is None:
             noise = randn_tensor(shape, generator=generator, device=device, dtype=dtype)
+            # if strength is 1. then initialise the latents to noise, else initial to image + noise
             latents = noise if is_strength_max else self.scheduler.add_noise(image_latents, noise, timestep)
+            # if pure noise then scale the initial latents by the  Scheduler's init sigma
+            latents = latents * self.scheduler.init_noise_sigma if is_strength_max else latents
         else:
             latents = latents.to(device)
 
-        # scale the initial noise by the standard deviation required by the scheduler
-        latents = latents * self.scheduler.init_noise_sigma
-
         outputs = (latents,)
 
         if return_noise: