Malformed JSON should return HTTP 400, not HTTP 500

Using the Stash REST API and sending POST or PUT requests, if the JSON payload is not formated correctly the Stash server returns HTTP 500 instead of HTTP 400.

• STEPS TO REPRODUCE
  curl -H "Authorization: Basic ..." -H "Content-Type: application/json" -X PUT -d ' " {hook-url-0" : "some-url"}

  ' 'https://example.com/rest/api/1.0/projects/

  {projectKey}

  /repos/

  {repositorySlug}

  /settings/hooks/

  {hookKey}

  /enabled

Note that the payload is not correct JSON.

• RESULTS
  Stash returns
  HTTP/1.1 500 Internal Server Error
  {
  "errors": [ { "context": null, "exceptionName": null, "message": "An error occurred while processing the request. Check the server logs for more information." }

  ]
  }

Stash should return,
400 Bad Request