Fix the issue with empty array replacement

[chengjingtao]

cherry-pick commit 95337e9 merged by tektoncd#5095 in release-0.37.x

Prior to this change, if there is only one element in an array that is
a reference to an empty array, the original array becomes nil after
replacement, but it should be an empty array instead of nil.

Fixes tektoncd#5149

Signed-off-by: Vincent Demeester [email protected]

Changes

Submitter Checklist

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Release Notes

After the replacement with an empty array, the original array will be empty.

Example:
---
params:
  - name: myarray
     value: "$(params.anEmptyArray[*])"

[chengjingtao]

Fix #29