Improve POST method management in case of no parameter entry in the post...

... data (no 'form-data' or 'x-www-form-urlencoded' contentType) but raw data like this kind of request:

POST HTTP/1.1
Host: 192.168.5.66:1881?action=setParamMonitor
Cache-Control: no-cache

{ "dests":[ "M*" ], "eraseAll":0, "paramMonitor":{ "numbers":{ "eraseAll":0, "groups":[ { "name":"Test de groupe", "data":[ { "label":"Data 1 & 3", "num":"1" }, { "label":"Data 2", "num":"2" } ] } ] } } }