Validate GatherND indices rank before access

[Akshay Sonawane (apsonawane)]

This pull request introduces a validation check in the GatherND operator to ensure that the indices tensor is not scalar (i.e., has rank greater than 0), and adds a corresponding unit test to verify the new error handling. This prevents invalid inputs from proceeding and improves the robustness of the operator.

Input validation improvements:

• Added a check in gather_nd.cc to return an error if the indices tensor has zero dimensions, with a clear error message.

Testing enhancements:

• Added a unit test GatherND_runtime_scalar_indices_error in gather_nd_op_test.cc to verify that passing a scalar indices tensor triggers the expected error.

[Copilot]

Pull request overview

Adds CPU GatherND runtime validation to reject scalar indices safely.

Changes:

• Validates indices rank before indexing its shape.
• Adds a CPU regression test for scalar indices.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
onnxruntime/core/providers/cpu/tensor/gather_nd.cc	Adds the rank validation.
onnxruntime/test/providers/cpu/tensor/gather_nd_op_test.cc	Tests runtime rejection of scalar indices.

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