Parse command arguments when not blank

[notherno]

What I changed

• Parsing of arguments JSON condition in executeCommand command
• Call of executeCommand function without arguments

Why

When we set StreamDeck action arguments (JSON) to blank, the payload structure from StreamDeck plugin is like following example:

Message received, ExecuteCommandMessage.: {"id":"ExecuteCommandMessage","data":"{\"command\":\"editor.action.formatDocument\",\"arguments\":\"\"}"}

This may cause following JSON parse error.

Uncaught SyntaxError: Unexpected end of JSON input`

This PR fixes this problem.

Related issues

fixes #35

[notherno]

The default value of commandArguments is undefined, thus this if statement should be unnecessary.