tf.square でのエラーについて

Question

TensorFlow 1.x で以下の定義で下記のエラーが出る場合、変数にはどのような値が入っていると考えられますか？

tf.square(ww)

（中略）
tf.square(ww)
File "/tensorflow-1.15.2/python3.6/tensorflow_core/python/ops/gen_math_ops.py", line 10929, in square
"Square", x=x, name=name)
File "/tensorflow-1.15.2/python3.6/tensorflow_core/python/framework/op_def_library.py", line 794, in _apply_op_helper
op_def=op_def)
File "/tensorflow-1.15.2/python3.6/tensorflow_core/python/util/deprecation.py", line 507, in new_func
return func(*args, **kwargs)
File "/tensorflow-1.15.2/python3.6/tensorflow_core/python/framework/ops.py", line 3357, in create_op
attrs, op_def, compute_device)
File "/tensorflow-1.15.2/python3.6/tensorflow_core/python/framework/ops.py", line 3426, in create_op_internal
op_def=op_def)
File "/tensorflow-1.15.2/python3.6/tensorflow