Fix empty raw responses parsed as json

src/protocols/Http.ts

@@ -1,9 +1,9 @@
 "use strict";
 
-import staticHttpRoutes from "./routes.json";
-import { KuzzleAbstractProtocol } from "./abstract/Base";
 import { HttpRoutes, JSONObject } from "../types";
 import { RequestPayload } from "../types/RequestPayload";
+import { KuzzleAbstractProtocol } from "./abstract/Base";
+import staticHttpRoutes from "./routes.json";
 
 /**
  * Http protocol used to connect to a Kuzzle server.
@@ -405,6 +405,10 @@ export default class HttpProtocol extends KuzzleAbstractProtocol {
             );
           }
 
+          if (response.body === "") {
+            return "";
+          }
+
           return JSON.parse(response.body);
         });
     }
@@ -435,6 +439,10 @@ export default class HttpProtocol extends KuzzleAbstractProtocol {
 
       xhr.onload = () => {
         try {
+          if (xhr.responseText === "") {
+            resolve("");
+          }
+
           const json = JSON.parse(xhr.responseText);
           resolve(json);
         } catch (err) {