clp-s: Add a comma after unstructured array fields during JSON serialization (fixes #410).

[wraymo]

References

#410

Description

The JSON serializer does not add a comma after an unstructured array field during decompression, which makes the decompressed log not in a valid JSON format. This PR fixes the bug.

Validation performed

Compressed the logs below and decompressed the archive

{"array":[1,2,3],"object":{"key":"value"}}
{"array":[4,5,6]}

Without the code change, the decompressed logs are

{"array":[1,2,3]"object":{"key":"value"}}
{"array":[4,5,6}

Now they are

{"array":[1,2,3],"object":{"key":"value"}}
{"array":[4,5,6]}

[kirkrodrigues]

Fine with the commit message, but can we open an issue and add (fixes XXX) to the message?

[wraymo]

Fine with the commit message, but can we open an issue and add (fixes XXX) to the message?

Sure