fix an issue in live previews that happens when you use SDXL with fp16 VAE

modules/processing.py

@@ -539,8 +539,7 @@ def create_random_tensors(shape, seeds, subseeds=None, subseed_strength=0.0, see
 
 
 def decode_first_stage(model, x):
-    with devices.autocast(disable=x.dtype == devices.dtype_vae):
-        x = model.decode_first_stage(x)
+    x = model.decode_first_stage(x.to(devices.dtype_vae))
 
     return x