In JsonStoreHandler, an empty string should be treated similarly to the null string

[minhhieugma]

In JsonStoreHandler, an empty string should be treated similarly to the null string.

• It is possible that we receive an empty JSON string.
• Of course, the senders should send a null value instead of an empty string.
• But we don't have a way to indicate that we only accept a null value. That's why we should handle the empty string case.

Improve ILogger usage

• The best practice is providing information that we use to make the message via parameters so that the log system can utilize this information later

[minhhieugma]

@Tailslide hi, any concern on this PR?

[Tailslide]

@Tailslide hi, any concern on this PR?

Hi no just haven’t had time to sit down in front of the PC yet and it didn’t look urgent. Thanks for your contributions!