Only apply ztSNR related code if alphas_cumprod exists

modules/processing.py

@@ -882,6 +882,7 @@ def process_images_inner(p: StableDiffusionProcessing) -> Processed:
                 alphas_bar[-1] = 4.8973451890853435e-08
                 return alphas_bar
 
+            if hasattr(p.sd_model, 'alphas_cumprod') and hasattr(p.sd_model, 'alphas_cumprod_original'):
                 p.sd_model.alphas_cumprod = p.sd_model.alphas_cumprod_original.to(shared.device)
 
                 if opts.use_downcasted_alpha_bar: