fix bugs related to cuda

cldm/ddim_hacked.py

@@ -16,7 +16,7 @@ class DDIMSampler(object):
 
     def register_buffer(self, name, attr):
         if type(attr) == torch.Tensor:
-            if attr.device != torch.device("cuda"):
+            if attr.device != torch.device("cuda") and torch.cuda.is_available():
                 attr = attr.to(torch.device("cuda"))
         setattr(self, name, attr)