[BugFix] Fix device initialization in CrossQLoss.maybe_init_target_entropy

Move device retrieval outside the 'if target_entropy == auto' block to ensure
the device is available when registering the target_entropy buffer.


ghstack-source-id: 515c3a6
Pull-Request: #3311

Author: vmoens

torchrl/objectives/crossq.py

@@ -374,8 +374,8 @@ def maybe_init_target_entropy(self, fault_tolerant=True):
         if "_target_entropy" in self._buffers:
             return
         target_entropy = self._target_entropy
+        device = next(self.parameters()).device
         if target_entropy == "auto":
-            device = next(self.parameters()).device
             action_spec = self.get_action_spec()
             if action_spec is None:
                 if fault_tolerant: