Pub/Sub can only publish JS truthy values

[akiroz]

Pub/Sub can only publish JS truthy values

• Skygear SDK Date/Version: 0.23.0

Expected Results

EITHER pubsub accept any serializable JS value
OR pubsub message requires a single Object/Array as per the JSON spec

Actual Results

skygear.pubsub.publish will throw an exception if the message body is JS falsey.
i.e. 42, "hello", [] and {} works but 0, "", and null does not.

[Steven-Chan]

@rickmak I suggest restricting the pubsub message to JSON object/dictionary only to make it consistent across all SDK.