Invalid json in case of failed load

[mcmorry]

engine/src/net/http.js

Line 372 in 18bdc36

response = JSON.parse(xhr.responseText);

If I try to load a JSON file and I have a loading error (for example "No Access-Control-Allow-Origin header is present") the xhr status is 0 and is considered as a success. I don't know if this is correct, but supposing it is, the result of the get request is an empty string that cannot be parsed:

Uncaught SyntaxError: Unexpected end of JSON input
at JSON.parse ()
at Object._onSuccess (playcanvas-stable.dbg.js:20204)
at Object._onReadyStateChange (playcanvas-stable.dbg.js:20174)
at Object. (playcanvas-stable.dbg.js:20138)

So a simple patch would be to check for a not empty string before parsing, but I'm not sure if it's not better to understand why the xhr status zero is considered a successful request.
I had also an issue when the network was off. The get method doesn't return an error, but a successful empty result.

[mcmorry]

Also, I would probably add a try catch around the JSON.parse and notify the exception as an error, so that it can be better handled by the application.