Adding fix for loss turning to nan

Signed-off-by: Shriti Priya <[email protected]>

Author: monshri

art/attacks/poisoning/sleeper_agent_attack.py

@@ -229,6 +229,11 @@ def poison(  # type: ignore
                 best_B = B_  # pylint: disable=C0103
                 best_x_poisoned = x_poisoned
                 best_indices_poison = self.indices_poison
+        if best_B == np.finfo(np.float32).max:
+            logger.warning("Attack unsuccessful: all loss values were non-finite. Defaulting to final trial.")
+            best_B = B_  # pylint: disable=C0103
+            best_x_poisoned = x_poisoned
+            best_indices_poison = self.indices_poison
 
         # Apply De-Normalization
         if isinstance(