Fix AJAX data source error

Fixes select2#4355

Verified in Firefox & Chromium

src/js/select2/data/ajax.js

@@ -82,7 +82,7 @@ define([
       }, function () {
         // Attempt to detect if a request was aborted
         // Only works if the transport exposes a status property
-        if ($request.status && $request.status === '0') {
+        if ('status' in $request && $request.status === 0) {
           return;
         }