Fix VAELoader (Comfy-Org#11880)

Author: comfyanonymous

nodes.py

@@ -788,6 +788,7 @@ def INPUT_TYPES(s):
 
     #TODO: scale factor?
     def load_vae(self, vae_name):
+        metadata = None
         if vae_name == "pixel_space":
             sd = {}
             sd["pixel_space_vae"] = torch.tensor(1.0)