[GraphBolt][CUDA] Handle edge case of %100 cache hit rate.

[mfbalin]

Description

When cache hit rate is %100, this function is called with 0-sized tensors. If it is called with empty tensors, then we do nothing and return as there is nothing to do.

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• I've leverage the tools to beautify the python and c++ code.
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• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change
• Related issue is referred in this PR
• If the PR is for a new model/paper, I've updated the example index here.

Changes

[dgl-bot]

To trigger regression tests:

• @dgl-bot run [instance-type] [which tests] [compare-with-branch];
  For example: @dgl-bot run g4dn.4xlarge all dmlc/master or @dgl-bot run c5.9xlarge kernel,api dmlc/master

[dgl-bot]

Commit ID: cdd60eb

Build ID: 1

Status: ⚪️ CI test cancelled due to overrun.

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[TristonC]

Confirmed the fix

[dgl-bot]

Commit ID: 441d74f

Build ID: 2

Status: ✅ CI test succeeded.

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