[brief] Few fixes.

[detailed]
- When looking up a key in the registry, if the key is not found it
  should raise an exception even if the suffix is none.
- Fixes a typo in EMA.

src/pyro/core/utils.py

@@ -295,6 +295,10 @@ def get(self, name: str, suffix: str | None = None) -> typing.Any:
                 raise KeyError(
                     f"No object called '{name}' found in the '{self._name}' registrar"
                 )
+        elif ret is None:
+            raise KeyError(
+                f"No object called '{name}' found in the '{self._name}' registrar"
+            )
         return ret
 
     def __contains__(self, name: str) -> bool:

src/pyro/model/networks.py

@@ -88,7 +88,7 @@ def _update(self, net: nn.Module, update_fn: typing.Callable) -> None:
             net.state_dict().values(),
             strict=True,
         ):
-            if self.device:
+            if self._device:
                 net_v = net_v.to(device=self.device)
             ema_v.copy_(update_fn(ema_v, net_v))