[Kernel] Fix einsum operator for empty inputs (#27226)
### Description
Dupe of #23379 - opening new PR to debug pending build issues before
merging
### Motivation and Context
Fix Einsum handling of empty inputs
Bug identification credit: @neNasko1
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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
