This fixes an issue we are seeing with benchmarks.

PiperOrigin-RevId: 286275744
Change-Id: Ie82e11c606bb65a0853c1432d1336cca290b636c
diff --git a/tensorflow/python/eager/context.py b/tensorflow/python/eager/context.py
index c7c3551..540ee87 100644
--- a/tensorflow/python/eager/context.py
+++ b/tensorflow/python/eager/context.py
@@ -1458,7 +1458,7 @@
     if policy is None:
       policy = MIRRORING_NONE
 
-    if self._mirroring_policy != policy:
+    if self._mirroring_policy is not None or self._mirroring_policy != policy:
       self._mirroring_policy = policy
 
       # Only set the policy if the context has already been initialized