Add conditional logic to improve functionality (#29015)
This pull request strengthens the validation logic for the
`block_row_indices` input in the SparseAttention operator and adds a
corresponding unit test to ensure that zero-dimension cases are properly
rejected.
Validation improvements:
* Updated the check in `Status CheckInputs` (in
`sparse_attention_helper.h`) to require that the first dimension of
`block_row_indices` is greater than zero, preventing invalid
zero-dimension input.
Test coverage:
* Added a new unit test `RejectsZeroDimBlockRowIndices` in
`sparse_attention_op_test.cc` to verify that the operator correctly
rejects inputs where `block_row_indices` has a zero in its first
dimension.
