[NumPy] Fix test failures under NumPy 1.25.

PiperOrigin-RevId: 549474788

Author: hawkinsp

tensorflow_model_optimization/python/core/internal/tensor_encoding/testing/test_utils.py

@@ -521,7 +521,7 @@ def evaluate_tf_py_list(self, fetches, session=None):
     for i, value in enumerate(eval_fetches):
       if isinstance(value, dict):
         eval_fetches[i] = py_utils.merge_dicts(value, py_fetches[i])
-      elif value == placeholder_empty_tuple:
+      elif isinstance(value, tuple) and value == placeholder_empty_tuple:
         eval_fetches[i] = py_fetches[i]
     return eval_fetches