Do not try to parse the body of 204 No Content responses

Since jQuery 1.9, 204 are acts as errors.

Fix both http://bugs.jquery.com/ticket/13292 and http://bugs.jquery.com/ticket/13261 .

I'm sorry to not add tests but I was not able to setup the test environment (PHP ...)

I already patched it in my app, it works fine.

Regards.