fix(request-transformer) an empty JSON array after being decoded, can…

[catbro666]

…'t be properly re-encoded as an array. Instead, it becomes an empty json object.

This PR fixes this issue. An empty json array will remain to be an empty json array after being decoded and re-encoded.

This is a sister PR to PR:

#4901

It contains a similar fix, but now to request-transformer (this plugin).

FTI-4205

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All committers have signed the CLA.

[catbro666]

done