Bug fix to disable lower recomposed sdpa (#4211)

Summary: Pull Request resolved: #4211

Reviewed By: digantdesai, mcr229

Differential Revision: D59640840

Pulled By: guangy10

fbshipit-source-id: 984dec35485b4396ace28310eb61376b7bbebd80

Author: guangy10

backends/xnnpack/partition/xnnpack_partitioner.py

@@ -869,7 +869,9 @@ def __init__(
         self.quant = quant
 
         # TODO(T174256335) - remove this once we have a better way to handle >2d Mask
-        self._lower_recomposed_sdpa: bool = _lower_recomposed_sdpa or True
+        self._lower_recomposed_sdpa: bool = (
+            _lower_recomposed_sdpa if _lower_recomposed_sdpa is not None else True
+        )
 
         self.delegation_spec = DelegationSpec(XnnpackBackend.__name__, [])
         self.partition_tags: Dict[str, DelegationSpec] = {}